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.azure-pipelines.ymlH A D05-Jul-202116.2 KiB455441

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MAINTAINERSH A D05-Jul-202132.6 KiB1,2491,132

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metadataH A D03-May-202266 54

README

1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see https://lists.denx.de/pipermail/u-boot and
55https://marc.info/?l=u-boot
56
57Where to get source code:
58=========================
59
60The U-Boot source code is maintained in the Git repository at
61https://source.denx.de/u-boot/u-boot.git ; you can browse it online at
62https://source.denx.de/u-boot/u-boot
63
64The "Tags" links on this page allow you to download tarballs of
65any version you might be interested in. Official releases are also
66available from the DENX file server through HTTPS or FTP.
67https://ftp.denx.de/pub/u-boot/
68ftp://ftp.denx.de/pub/u-boot/
69
70
71Where we come from:
72===================
73
74- start from 8xxrom sources
75- create PPCBoot project (https://sourceforge.net/projects/ppcboot)
76- clean up code
77- make it easier to add custom boards
78- make it possible to add other [PowerPC] CPUs
79- extend functions, especially:
80  * Provide extended interface to Linux boot loader
81  * S-Record download
82  * network boot
83  * ATA disk / SCSI ... boot
84- create ARMBoot project (https://sourceforge.net/projects/armboot)
85- add other CPU families (starting with ARM)
86- create U-Boot project (https://sourceforge.net/projects/u-boot)
87- current project page: see https://www.denx.de/wiki/U-Boot
88
89
90Names and Spelling:
91===================
92
93The "official" name of this project is "Das U-Boot". The spelling
94"U-Boot" shall be used in all written text (documentation, comments
95in source files etc.). Example:
96
97	This is the README file for the U-Boot project.
98
99File names etc. shall be based on the string "u-boot". Examples:
100
101	include/asm-ppc/u-boot.h
102
103	#include <asm/u-boot.h>
104
105Variable names, preprocessor constants etc. shall be either based on
106the string "u_boot" or on "U_BOOT". Example:
107
108	U_BOOT_VERSION		u_boot_logo
109	IH_OS_U_BOOT		u_boot_hush_start
110
111
112Versioning:
113===========
114
115Starting with the release in October 2008, the names of the releases
116were changed from numerical release numbers without deeper meaning
117into a time stamp based numbering. Regular releases are identified by
118names consisting of the calendar year and month of the release date.
119Additional fields (if present) indicate release candidates or bug fix
120releases in "stable" maintenance trees.
121
122Examples:
123	U-Boot v2009.11	    - Release November 2009
124	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
125	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
126
127
128Directory Hierarchy:
129====================
130
131/arch			Architecture specific files
132  /arc			Files generic to ARC architecture
133  /arm			Files generic to ARM architecture
134  /m68k			Files generic to m68k architecture
135  /microblaze		Files generic to microblaze architecture
136  /mips			Files generic to MIPS architecture
137  /nds32		Files generic to NDS32 architecture
138  /nios2		Files generic to Altera NIOS2 architecture
139  /powerpc		Files generic to PowerPC architecture
140  /riscv		Files generic to RISC-V architecture
141  /sandbox		Files generic to HW-independent "sandbox"
142  /sh			Files generic to SH architecture
143  /x86			Files generic to x86 architecture
144  /xtensa		Files generic to Xtensa architecture
145/api			Machine/arch independent API for external apps
146/board			Board dependent files
147/cmd			U-Boot commands functions
148/common			Misc architecture independent functions
149/configs		Board default configuration files
150/disk			Code for disk drive partition handling
151/doc			Documentation (don't expect too much)
152/drivers		Commonly used device drivers
153/dts			Contains Makefile for building internal U-Boot fdt.
154/env			Environment files
155/examples		Example code for standalone applications, etc.
156/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
157/include		Header Files
158/lib			Library routines generic to all architectures
159/Licenses		Various license files
160/net			Networking code
161/post			Power On Self Test
162/scripts		Various build scripts and Makefiles
163/test			Various unit test files
164/tools			Tools to build S-Record or U-Boot images, etc.
165
166Software Configuration:
167=======================
168
169Configuration is usually done using C preprocessor defines; the
170rationale behind that is to avoid dead code whenever possible.
171
172There are two classes of configuration variables:
173
174* Configuration _OPTIONS_:
175  These are selectable by the user and have names beginning with
176  "CONFIG_".
177
178* Configuration _SETTINGS_:
179  These depend on the hardware etc. and should not be meddled with if
180  you don't know what you're doing; they have names beginning with
181  "CONFIG_SYS_".
182
183Previously, all configuration was done by hand, which involved creating
184symbolic links and editing configuration files manually. More recently,
185U-Boot has added the Kbuild infrastructure used by the Linux kernel,
186allowing you to use the "make menuconfig" command to configure your
187build.
188
189
190Selection of Processor Architecture and Board Type:
191---------------------------------------------------
192
193For all supported boards there are ready-to-use default
194configurations available; just type "make <board_name>_defconfig".
195
196Example: For a TQM823L module type:
197
198	cd u-boot
199	make TQM823L_defconfig
200
201Note: If you're looking for the default configuration file for a board
202you're sure used to be there but is now missing, check the file
203doc/README.scrapyard for a list of no longer supported boards.
204
205Sandbox Environment:
206--------------------
207
208U-Boot can be built natively to run on a Linux host using the 'sandbox'
209board. This allows feature development which is not board- or architecture-
210specific to be undertaken on a native platform. The sandbox is also used to
211run some of U-Boot's tests.
212
213See doc/arch/sandbox.rst for more details.
214
215
216Board Initialisation Flow:
217--------------------------
218
219This is the intended start-up flow for boards. This should apply for both
220SPL and U-Boot proper (i.e. they both follow the same rules).
221
222Note: "SPL" stands for "Secondary Program Loader," which is explained in
223more detail later in this file.
224
225At present, SPL mostly uses a separate code path, but the function names
226and roles of each function are the same. Some boards or architectures
227may not conform to this.  At least most ARM boards which use
228CONFIG_SPL_FRAMEWORK conform to this.
229
230Execution typically starts with an architecture-specific (and possibly
231CPU-specific) start.S file, such as:
232
233	- arch/arm/cpu/armv7/start.S
234	- arch/powerpc/cpu/mpc83xx/start.S
235	- arch/mips/cpu/start.S
236
237and so on. From there, three functions are called; the purpose and
238limitations of each of these functions are described below.
239
240lowlevel_init():
241	- purpose: essential init to permit execution to reach board_init_f()
242	- no global_data or BSS
243	- there is no stack (ARMv7 may have one but it will soon be removed)
244	- must not set up SDRAM or use console
245	- must only do the bare minimum to allow execution to continue to
246		board_init_f()
247	- this is almost never needed
248	- return normally from this function
249
250board_init_f():
251	- purpose: set up the machine ready for running board_init_r():
252		i.e. SDRAM and serial UART
253	- global_data is available
254	- stack is in SRAM
255	- BSS is not available, so you cannot use global/static variables,
256		only stack variables and global_data
257
258	Non-SPL-specific notes:
259	- dram_init() is called to set up DRAM. If already done in SPL this
260		can do nothing
261
262	SPL-specific notes:
263	- you can override the entire board_init_f() function with your own
264		version as needed.
265	- preloader_console_init() can be called here in extremis
266	- should set up SDRAM, and anything needed to make the UART work
267	- there is no need to clear BSS, it will be done by crt0.S
268	- for specific scenarios on certain architectures an early BSS *can*
269	  be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
270	  of BSS prior to entering board_init_f()) but doing so is discouraged.
271	  Instead it is strongly recommended to architect any code changes
272	  or additions such to not depend on the availability of BSS during
273	  board_init_f() as indicated in other sections of this README to
274	  maintain compatibility and consistency across the entire code base.
275	- must return normally from this function (don't call board_init_r()
276		directly)
277
278Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
279this point the stack and global_data are relocated to below
280CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
281memory.
282
283board_init_r():
284	- purpose: main execution, common code
285	- global_data is available
286	- SDRAM is available
287	- BSS is available, all static/global variables can be used
288	- execution eventually continues to main_loop()
289
290	Non-SPL-specific notes:
291	- U-Boot is relocated to the top of memory and is now running from
292		there.
293
294	SPL-specific notes:
295	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
296		CONFIG_SPL_STACK_R_ADDR points into SDRAM
297	- preloader_console_init() can be called here - typically this is
298		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
299		spl_board_init() function containing this call
300	- loads U-Boot or (in falcon mode) Linux
301
302
303
304Configuration Options:
305----------------------
306
307Configuration depends on the combination of board and CPU type; all
308such information is kept in a configuration file
309"include/configs/<board_name>.h".
310
311Example: For a TQM823L module, all configuration settings are in
312"include/configs/TQM823L.h".
313
314
315Many of the options are named exactly as the corresponding Linux
316kernel configuration options. The intention is to make it easier to
317build a config tool - later.
318
319- ARM Platform Bus Type(CCI):
320		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
321		provides full cache coherency between two clusters of multi-core
322		CPUs and I/O coherency for devices and I/O masters
323
324		CONFIG_SYS_FSL_HAS_CCI400
325
326		Defined For SoC that has cache coherent interconnect
327		CCN-400
328
329		CONFIG_SYS_FSL_HAS_CCN504
330
331		Defined for SoC that has cache coherent interconnect CCN-504
332
333The following options need to be configured:
334
335- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
336
337- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
338
339- 85xx CPU Options:
340		CONFIG_SYS_PPC64
341
342		Specifies that the core is a 64-bit PowerPC implementation (implements
343		the "64" category of the Power ISA). This is necessary for ePAPR
344		compliance, among other possible reasons.
345
346		CONFIG_SYS_FSL_TBCLK_DIV
347
348		Defines the core time base clock divider ratio compared to the
349		system clock.  On most PQ3 devices this is 8, on newer QorIQ
350		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
351
352		CONFIG_SYS_FSL_PCIE_COMPAT
353
354		Defines the string to utilize when trying to match PCIe device
355		tree nodes for the given platform.
356
357		CONFIG_SYS_FSL_ERRATUM_A004510
358
359		Enables a workaround for erratum A004510.  If set,
360		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
361		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
362
363		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
364		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
365
366		Defines one or two SoC revisions (low 8 bits of SVR)
367		for which the A004510 workaround should be applied.
368
369		The rest of SVR is either not relevant to the decision
370		of whether the erratum is present (e.g. p2040 versus
371		p2041) or is implied by the build target, which controls
372		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
373
374		See Freescale App Note 4493 for more information about
375		this erratum.
376
377		CONFIG_A003399_NOR_WORKAROUND
378		Enables a workaround for IFC erratum A003399. It is only
379		required during NOR boot.
380
381		CONFIG_A008044_WORKAROUND
382		Enables a workaround for T1040/T1042 erratum A008044. It is only
383		required during NAND boot and valid for Rev 1.0 SoC revision
384
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
386
387		This is the value to write into CCSR offset 0x18600
388		according to the A004510 workaround.
389
390		CONFIG_SYS_FSL_DSP_DDR_ADDR
391		This value denotes start offset of DDR memory which is
392		connected exclusively to the DSP cores.
393
394		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
395		This value denotes start offset of M2 memory
396		which is directly connected to the DSP core.
397
398		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
399		This value denotes start offset of M3 memory which is directly
400		connected to the DSP core.
401
402		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
403		This value denotes start offset of DSP CCSR space.
404
405		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
406		Single Source Clock is clocking mode present in some of FSL SoC's.
407		In this mode, a single differential clock is used to supply
408		clocks to the sysclock, ddrclock and usbclock.
409
410		CONFIG_SYS_CPC_REINIT_F
411		This CONFIG is defined when the CPC is configured as SRAM at the
412		time of U-Boot entry and is required to be re-initialized.
413
414		CONFIG_DEEP_SLEEP
415		Indicates this SoC supports deep sleep feature. If deep sleep is
416		supported, core will start to execute uboot when wakes up.
417
418- Generic CPU options:
419		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
420
421		Defines the endianess of the CPU. Implementation of those
422		values is arch specific.
423
424		CONFIG_SYS_FSL_DDR
425		Freescale DDR driver in use. This type of DDR controller is
426		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
427		SoCs.
428
429		CONFIG_SYS_FSL_DDR_ADDR
430		Freescale DDR memory-mapped register base.
431
432		CONFIG_SYS_FSL_DDR_EMU
433		Specify emulator support for DDR. Some DDR features such as
434		deskew training are not available.
435
436		CONFIG_SYS_FSL_DDRC_GEN1
437		Freescale DDR1 controller.
438
439		CONFIG_SYS_FSL_DDRC_GEN2
440		Freescale DDR2 controller.
441
442		CONFIG_SYS_FSL_DDRC_GEN3
443		Freescale DDR3 controller.
444
445		CONFIG_SYS_FSL_DDRC_GEN4
446		Freescale DDR4 controller.
447
448		CONFIG_SYS_FSL_DDRC_ARM_GEN3
449		Freescale DDR3 controller for ARM-based SoCs.
450
451		CONFIG_SYS_FSL_DDR1
452		Board config to use DDR1. It can be enabled for SoCs with
453		Freescale DDR1 or DDR2 controllers, depending on the board
454		implemetation.
455
456		CONFIG_SYS_FSL_DDR2
457		Board config to use DDR2. It can be enabled for SoCs with
458		Freescale DDR2 or DDR3 controllers, depending on the board
459		implementation.
460
461		CONFIG_SYS_FSL_DDR3
462		Board config to use DDR3. It can be enabled for SoCs with
463		Freescale DDR3 or DDR3L controllers.
464
465		CONFIG_SYS_FSL_DDR3L
466		Board config to use DDR3L. It can be enabled for SoCs with
467		DDR3L controllers.
468
469		CONFIG_SYS_FSL_DDR4
470		Board config to use DDR4. It can be enabled for SoCs with
471		DDR4 controllers.
472
473		CONFIG_SYS_FSL_IFC_BE
474		Defines the IFC controller register space as Big Endian
475
476		CONFIG_SYS_FSL_IFC_LE
477		Defines the IFC controller register space as Little Endian
478
479		CONFIG_SYS_FSL_IFC_CLK_DIV
480		Defines divider of platform clock(clock input to IFC controller).
481
482		CONFIG_SYS_FSL_LBC_CLK_DIV
483		Defines divider of platform clock(clock input to eLBC controller).
484
485		CONFIG_SYS_FSL_PBL_PBI
486		It enables addition of RCW (Power on reset configuration) in built image.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SYS_FSL_PBL_RCW
490		It adds PBI(pre-boot instructions) commands in u-boot build image.
491		PBI commands can be used to configure SoC before it starts the execution.
492		Please refer doc/README.pblimage for more details
493
494		CONFIG_SYS_FSL_DDR_BE
495		Defines the DDR controller register space as Big Endian
496
497		CONFIG_SYS_FSL_DDR_LE
498		Defines the DDR controller register space as Little Endian
499
500		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
501		Physical address from the view of DDR controllers. It is the
502		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
503		it could be different for ARM SoCs.
504
505		CONFIG_SYS_FSL_DDR_INTLV_256B
506		DDR controller interleaving on 256-byte. This is a special
507		interleaving mode, handled by Dickens for Freescale layerscape
508		SoCs with ARM core.
509
510		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
511		Number of controllers used as main memory.
512
513		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
514		Number of controllers used for other than main memory.
515
516		CONFIG_SYS_FSL_HAS_DP_DDR
517		Defines the SoC has DP-DDR used for DPAA.
518
519		CONFIG_SYS_FSL_SEC_BE
520		Defines the SEC controller register space as Big Endian
521
522		CONFIG_SYS_FSL_SEC_LE
523		Defines the SEC controller register space as Little Endian
524
525- MIPS CPU options:
526		CONFIG_SYS_INIT_SP_OFFSET
527
528		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
529		pointer. This is needed for the temporary stack before
530		relocation.
531
532		CONFIG_XWAY_SWAP_BYTES
533
534		Enable compilation of tools/xway-swap-bytes needed for Lantiq
535		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
536		be swapped if a flash programmer is used.
537
538- ARM options:
539		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
540
541		Select high exception vectors of the ARM core, e.g., do not
542		clear the V bit of the c1 register of CP15.
543
544		COUNTER_FREQUENCY
545		Generic timer clock source frequency.
546
547		COUNTER_FREQUENCY_REAL
548		Generic timer clock source frequency if the real clock is
549		different from COUNTER_FREQUENCY, and can only be determined
550		at run time.
551
552- Tegra SoC options:
553		CONFIG_TEGRA_SUPPORT_NON_SECURE
554
555		Support executing U-Boot in non-secure (NS) mode. Certain
556		impossible actions will be skipped if the CPU is in NS mode,
557		such as ARM architectural timer initialization.
558
559- Linux Kernel Interface:
560		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
561
562		When transferring memsize parameter to Linux, some versions
563		expect it to be in bytes, others in MB.
564		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
565
566		CONFIG_OF_LIBFDT
567
568		New kernel versions are expecting firmware settings to be
569		passed using flattened device trees (based on open firmware
570		concepts).
571
572		CONFIG_OF_LIBFDT
573		 * New libfdt-based support
574		 * Adds the "fdt" command
575		 * The bootm command automatically updates the fdt
576
577		OF_TBCLK - The timebase frequency.
578
579		boards with QUICC Engines require OF_QE to set UCC MAC
580		addresses
581
582		CONFIG_OF_BOARD_SETUP
583
584		Board code has addition modification that it wants to make
585		to the flat device tree before handing it off to the kernel
586
587		CONFIG_OF_SYSTEM_SETUP
588
589		Other code has addition modification that it wants to make
590		to the flat device tree before handing it off to the kernel.
591		This causes ft_system_setup() to be called before booting
592		the kernel.
593
594		CONFIG_OF_IDE_FIXUP
595
596		U-Boot can detect if an IDE device is present or not.
597		If not, and this new config option is activated, U-Boot
598		removes the ATA node from the DTS before booting Linux,
599		so the Linux IDE driver does not probe the device and
600		crash. This is needed for buggy hardware (uc101) where
601		no pull down resistor is connected to the signal IDE5V_DD7.
602
603		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
604
605		This setting is mandatory for all boards that have only one
606		machine type and must be used to specify the machine type
607		number as it appears in the ARM machine registry
608		(see https://www.arm.linux.org.uk/developer/machines/).
609		Only boards that have multiple machine types supported
610		in a single configuration file and the machine type is
611		runtime discoverable, do not have to use this setting.
612
613- vxWorks boot parameters:
614
615		bootvx constructs a valid bootline using the following
616		environments variables: bootdev, bootfile, ipaddr, netmask,
617		serverip, gatewayip, hostname, othbootargs.
618		It loads the vxWorks image pointed bootfile.
619
620		Note: If a "bootargs" environment is defined, it will override
621		the defaults discussed just above.
622
623- Cache Configuration:
624		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
625
626- Cache Configuration for ARM:
627		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
628				      controller
629		CONFIG_SYS_PL310_BASE - Physical base address of PL310
630					controller register space
631
632- Serial Ports:
633		CONFIG_PL010_SERIAL
634
635		Define this if you want support for Amba PrimeCell PL010 UARTs.
636
637		CONFIG_PL011_SERIAL
638
639		Define this if you want support for Amba PrimeCell PL011 UARTs.
640
641		CONFIG_PL011_CLOCK
642
643		If you have Amba PrimeCell PL011 UARTs, set this variable to
644		the clock speed of the UARTs.
645
646		CONFIG_PL01x_PORTS
647
648		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
649		define this to a list of base addresses for each (supported)
650		port. See e.g. include/configs/versatile.h
651
652		CONFIG_SERIAL_HW_FLOW_CONTROL
653
654		Define this variable to enable hw flow control in serial driver.
655		Current user of this option is drivers/serial/nsl16550.c driver
656
657- Autoboot Command:
658		CONFIG_BOOTCOMMAND
659		Only needed when CONFIG_BOOTDELAY is enabled;
660		define a command string that is automatically executed
661		when no character is read on the console interface
662		within "Boot Delay" after reset.
663
664		CONFIG_RAMBOOT and CONFIG_NFSBOOT
665		The value of these goes into the environment as
666		"ramboot" and "nfsboot" respectively, and can be used
667		as a convenience, when switching between booting from
668		RAM and NFS.
669
670- Serial Download Echo Mode:
671		CONFIG_LOADS_ECHO
672		If defined to 1, all characters received during a
673		serial download (using the "loads" command) are
674		echoed back. This might be needed by some terminal
675		emulations (like "cu"), but may as well just take
676		time on others. This setting #define's the initial
677		value of the "loads_echo" environment variable.
678
679- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
680		CONFIG_KGDB_BAUDRATE
681		Select one of the baudrates listed in
682		CONFIG_SYS_BAUDRATE_TABLE, see below.
683
684- Removal of commands
685		If no commands are needed to boot, you can disable
686		CONFIG_CMDLINE to remove them. In this case, the command line
687		will not be available, and when U-Boot wants to execute the
688		boot command (on start-up) it will call board_run_command()
689		instead. This can reduce image size significantly for very
690		simple boot procedures.
691
692- Regular expression support:
693		CONFIG_REGEX
694		If this variable is defined, U-Boot is linked against
695		the SLRE (Super Light Regular Expression) library,
696		which adds regex support to some commands, as for
697		example "env grep" and "setexpr".
698
699- Device tree:
700		CONFIG_OF_CONTROL
701		If this variable is defined, U-Boot will use a device tree
702		to configure its devices, instead of relying on statically
703		compiled #defines in the board file. This option is
704		experimental and only available on a few boards. The device
705		tree is available in the global data as gd->fdt_blob.
706
707		U-Boot needs to get its device tree from somewhere. This can
708		be done using one of the three options below:
709
710		CONFIG_OF_EMBED
711		If this variable is defined, U-Boot will embed a device tree
712		binary in its image. This device tree file should be in the
713		board directory and called <soc>-<board>.dts. The binary file
714		is then picked up in board_init_f() and made available through
715		the global data structure as gd->fdt_blob.
716
717		CONFIG_OF_SEPARATE
718		If this variable is defined, U-Boot will build a device tree
719		binary. It will be called u-boot.dtb. Architecture-specific
720		code will locate it at run-time. Generally this works by:
721
722			cat u-boot.bin u-boot.dtb >image.bin
723
724		and in fact, U-Boot does this for you, creating a file called
725		u-boot-dtb.bin which is useful in the common case. You can
726		still use the individual files if you need something more
727		exotic.
728
729		CONFIG_OF_BOARD
730		If this variable is defined, U-Boot will use the device tree
731		provided by the board at runtime instead of embedding one with
732		the image. Only boards defining board_fdt_blob_setup() support
733		this option (see include/fdtdec.h file).
734
735- Watchdog:
736		CONFIG_WATCHDOG
737		If this variable is defined, it enables watchdog
738		support for the SoC. There must be support in the SoC
739		specific code for a watchdog. For the 8xx
740		CPUs, the SIU Watchdog feature is enabled in the SYPCR
741		register.  When supported for a specific SoC is
742		available, then no further board specific code should
743		be needed to use it.
744
745		CONFIG_HW_WATCHDOG
746		When using a watchdog circuitry external to the used
747		SoC, then define this variable and provide board
748		specific code for the "hw_watchdog_reset" function.
749
750		CONFIG_SYS_WATCHDOG_FREQ
751		Some platforms automatically call WATCHDOG_RESET()
752		from the timer interrupt handler every
753		CONFIG_SYS_WATCHDOG_FREQ interrupts. If not set by the
754		board configuration file, a default of CONFIG_SYS_HZ/2
755		(i.e. 500) is used. Setting CONFIG_SYS_WATCHDOG_FREQ
756		to 0 disables calling WATCHDOG_RESET() from the timer
757		interrupt.
758
759- Real-Time Clock:
760
761		When CONFIG_CMD_DATE is selected, the type of the RTC
762		has to be selected, too. Define exactly one of the
763		following options:
764
765		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
766		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
767		CONFIG_RTC_MC146818	- use MC146818 RTC
768		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
769		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
770		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
771		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
772		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
773		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
774		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
775		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
776		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
777					  RV3029 RTC.
778
779		Note that if the RTC uses I2C, then the I2C interface
780		must also be configured. See I2C Support, below.
781
782- GPIO Support:
783		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
784
785		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
786		chip-ngpio pairs that tell the PCA953X driver the number of
787		pins supported by a particular chip.
788
789		Note that if the GPIO device uses I2C, then the I2C interface
790		must also be configured. See I2C Support, below.
791
792- I/O tracing:
793		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
794		accesses and can checksum them or write a list of them out
795		to memory. See the 'iotrace' command for details. This is
796		useful for testing device drivers since it can confirm that
797		the driver behaves the same way before and after a code
798		change. Currently this is supported on sandbox and arm. To
799		add support for your architecture, add '#include <iotrace.h>'
800		to the bottom of arch/<arch>/include/asm/io.h and test.
801
802		Example output from the 'iotrace stats' command is below.
803		Note that if the trace buffer is exhausted, the checksum will
804		still continue to operate.
805
806			iotrace is enabled
807			Start:  10000000	(buffer start address)
808			Size:   00010000	(buffer size)
809			Offset: 00000120	(current buffer offset)
810			Output: 10000120	(start + offset)
811			Count:  00000018	(number of trace records)
812			CRC32:  9526fb66	(CRC32 of all trace records)
813
814- Timestamp Support:
815
816		When CONFIG_TIMESTAMP is selected, the timestamp
817		(date and time) of an image is printed by image
818		commands like bootm or iminfo. This option is
819		automatically enabled when you select CONFIG_CMD_DATE .
820
821- Partition Labels (disklabels) Supported:
822		Zero or more of the following:
823		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
824		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
825		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
826				       bootloader.  Note 2TB partition limit; see
827				       disk/part_efi.c
828		CONFIG_SCSI) you must configure support for at
829		least one non-MTD partition type as well.
830
831- IDE Reset method:
832		CONFIG_IDE_RESET_ROUTINE - this is defined in several
833		board configurations files but used nowhere!
834
835		CONFIG_IDE_RESET - is this is defined, IDE Reset will
836		be performed by calling the function
837			ide_set_reset(int reset)
838		which has to be defined in a board specific file
839
840- ATAPI Support:
841		CONFIG_ATAPI
842
843		Set this to enable ATAPI support.
844
845- LBA48 Support
846		CONFIG_LBA48
847
848		Set this to enable support for disks larger than 137GB
849		Also look at CONFIG_SYS_64BIT_LBA.
850		Whithout these , LBA48 support uses 32bit variables and will 'only'
851		support disks up to 2.1TB.
852
853		CONFIG_SYS_64BIT_LBA:
854			When enabled, makes the IDE subsystem use 64bit sector addresses.
855			Default is 32bit.
856
857- SCSI Support:
858		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
859		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
860		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
861		maximum numbers of LUNs, SCSI ID's and target
862		devices.
863
864		The environment variable 'scsidevs' is set to the number of
865		SCSI devices found during the last scan.
866
867- NETWORK Support (PCI):
868		CONFIG_E1000
869		Support for Intel 8254x/8257x gigabit chips.
870
871		CONFIG_E1000_SPI
872		Utility code for direct access to the SPI bus on Intel 8257x.
873		This does not do anything useful unless you set at least one
874		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
875
876		CONFIG_E1000_SPI_GENERIC
877		Allow generic access to the SPI bus on the Intel 8257x, for
878		example with the "sspi" command.
879
880		CONFIG_NATSEMI
881		Support for National dp83815 chips.
882
883		CONFIG_NS8382X
884		Support for National dp8382[01] gigabit chips.
885
886- NETWORK Support (other):
887
888		CONFIG_DRIVER_AT91EMAC
889		Support for AT91RM9200 EMAC.
890
891			CONFIG_RMII
892			Define this to use reduced MII inteface
893
894			CONFIG_DRIVER_AT91EMAC_QUIET
895			If this defined, the driver is quiet.
896			The driver doen't show link status messages.
897
898		CONFIG_CALXEDA_XGMAC
899		Support for the Calxeda XGMAC device
900
901		CONFIG_LAN91C96
902		Support for SMSC's LAN91C96 chips.
903
904			CONFIG_LAN91C96_USE_32_BIT
905			Define this to enable 32 bit addressing
906
907		CONFIG_SMC91111
908		Support for SMSC's LAN91C111 chip
909
910			CONFIG_SMC91111_BASE
911			Define this to hold the physical address
912			of the device (I/O space)
913
914			CONFIG_SMC_USE_32_BIT
915			Define this if data bus is 32 bits
916
917			CONFIG_SMC_USE_IOFUNCS
918			Define this to use i/o functions instead of macros
919			(some hardware wont work with macros)
920
921			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
922			Define this if you have more then 3 PHYs.
923
924		CONFIG_FTGMAC100
925		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
926
927			CONFIG_FTGMAC100_EGIGA
928			Define this to use GE link update with gigabit PHY.
929			Define this if FTGMAC100 is connected to gigabit PHY.
930			If your system has 10/100 PHY only, it might not occur
931			wrong behavior. Because PHY usually return timeout or
932			useless data when polling gigabit status and gigabit
933			control registers. This behavior won't affect the
934			correctnessof 10/100 link speed update.
935
936		CONFIG_SH_ETHER
937		Support for Renesas on-chip Ethernet controller
938
939			CONFIG_SH_ETHER_USE_PORT
940			Define the number of ports to be used
941
942			CONFIG_SH_ETHER_PHY_ADDR
943			Define the ETH PHY's address
944
945			CONFIG_SH_ETHER_CACHE_WRITEBACK
946			If this option is set, the driver enables cache flush.
947
948- TPM Support:
949		CONFIG_TPM
950		Support TPM devices.
951
952		CONFIG_TPM_TIS_INFINEON
953		Support for Infineon i2c bus TPM devices. Only one device
954		per system is supported at this time.
955
956			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
957			Define the burst count bytes upper limit
958
959		CONFIG_TPM_ST33ZP24
960		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
961
962			CONFIG_TPM_ST33ZP24_I2C
963			Support for STMicroelectronics ST33ZP24 I2C devices.
964			Requires TPM_ST33ZP24 and I2C.
965
966			CONFIG_TPM_ST33ZP24_SPI
967			Support for STMicroelectronics ST33ZP24 SPI devices.
968			Requires TPM_ST33ZP24 and SPI.
969
970		CONFIG_TPM_ATMEL_TWI
971		Support for Atmel TWI TPM device. Requires I2C support.
972
973		CONFIG_TPM_TIS_LPC
974		Support for generic parallel port TPM devices. Only one device
975		per system is supported at this time.
976
977			CONFIG_TPM_TIS_BASE_ADDRESS
978			Base address where the generic TPM device is mapped
979			to. Contemporary x86 systems usually map it at
980			0xfed40000.
981
982		CONFIG_TPM
983		Define this to enable the TPM support library which provides
984		functional interfaces to some TPM commands.
985		Requires support for a TPM device.
986
987		CONFIG_TPM_AUTH_SESSIONS
988		Define this to enable authorized functions in the TPM library.
989		Requires CONFIG_TPM and CONFIG_SHA1.
990
991- USB Support:
992		At the moment only the UHCI host controller is
993		supported (PIP405, MIP405); define
994		CONFIG_USB_UHCI to enable it.
995		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
996		and define CONFIG_USB_STORAGE to enable the USB
997		storage devices.
998		Note:
999		Supported are USB Keyboards and USB Floppy drives
1000		(TEAC FD-05PUB).
1001
1002		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1003		txfilltuning field in the EHCI controller on reset.
1004
1005		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1006		HW module registers.
1007
1008- USB Device:
1009		Define the below if you wish to use the USB console.
1010		Once firmware is rebuilt from a serial console issue the
1011		command "setenv stdin usbtty; setenv stdout usbtty" and
1012		attach your USB cable. The Unix command "dmesg" should print
1013		it has found a new device. The environment variable usbtty
1014		can be set to gserial or cdc_acm to enable your device to
1015		appear to a USB host as a Linux gserial device or a
1016		Common Device Class Abstract Control Model serial device.
1017		If you select usbtty = gserial you should be able to enumerate
1018		a Linux host by
1019		# modprobe usbserial vendor=0xVendorID product=0xProductID
1020		else if using cdc_acm, simply setting the environment
1021		variable usbtty to be cdc_acm should suffice. The following
1022		might be defined in YourBoardName.h
1023
1024			CONFIG_USB_DEVICE
1025			Define this to build a UDC device
1026
1027			CONFIG_USB_TTY
1028			Define this to have a tty type of device available to
1029			talk to the UDC device
1030
1031			CONFIG_USBD_HS
1032			Define this to enable the high speed support for usb
1033			device and usbtty. If this feature is enabled, a routine
1034			int is_usbd_high_speed(void)
1035			also needs to be defined by the driver to dynamically poll
1036			whether the enumeration has succeded at high speed or full
1037			speed.
1038
1039			CONFIG_SYS_CONSOLE_IS_IN_ENV
1040			Define this if you want stdin, stdout &/or stderr to
1041			be set to usbtty.
1042
1043		If you have a USB-IF assigned VendorID then you may wish to
1044		define your own vendor specific values either in BoardName.h
1045		or directly in usbd_vendor_info.h. If you don't define
1046		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1047		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1048		should pretend to be a Linux device to it's target host.
1049
1050			CONFIG_USBD_MANUFACTURER
1051			Define this string as the name of your company for
1052			- CONFIG_USBD_MANUFACTURER "my company"
1053
1054			CONFIG_USBD_PRODUCT_NAME
1055			Define this string as the name of your product
1056			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1057
1058			CONFIG_USBD_VENDORID
1059			Define this as your assigned Vendor ID from the USB
1060			Implementors Forum. This *must* be a genuine Vendor ID
1061			to avoid polluting the USB namespace.
1062			- CONFIG_USBD_VENDORID 0xFFFF
1063
1064			CONFIG_USBD_PRODUCTID
1065			Define this as the unique Product ID
1066			for your device
1067			- CONFIG_USBD_PRODUCTID 0xFFFF
1068
1069- ULPI Layer Support:
1070		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1071		the generic ULPI layer. The generic layer accesses the ULPI PHY
1072		via the platform viewport, so you need both the genric layer and
1073		the viewport enabled. Currently only Chipidea/ARC based
1074		viewport is supported.
1075		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1076		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1077		If your ULPI phy needs a different reference clock than the
1078		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1079		the appropriate value in Hz.
1080
1081- MMC Support:
1082		The MMC controller on the Intel PXA is supported. To
1083		enable this define CONFIG_MMC. The MMC can be
1084		accessed from the boot prompt by mapping the device
1085		to physical memory similar to flash. Command line is
1086		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1087		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1088
1089		CONFIG_SH_MMCIF
1090		Support for Renesas on-chip MMCIF controller
1091
1092			CONFIG_SH_MMCIF_ADDR
1093			Define the base address of MMCIF registers
1094
1095			CONFIG_SH_MMCIF_CLK
1096			Define the clock frequency for MMCIF
1097
1098- USB Device Firmware Update (DFU) class support:
1099		CONFIG_DFU_OVER_USB
1100		This enables the USB portion of the DFU USB class
1101
1102		CONFIG_DFU_NAND
1103		This enables support for exposing NAND devices via DFU.
1104
1105		CONFIG_DFU_RAM
1106		This enables support for exposing RAM via DFU.
1107		Note: DFU spec refer to non-volatile memory usage, but
1108		allow usages beyond the scope of spec - here RAM usage,
1109		one that would help mostly the developer.
1110
1111		CONFIG_SYS_DFU_DATA_BUF_SIZE
1112		Dfu transfer uses a buffer before writing data to the
1113		raw storage device. Make the size (in bytes) of this buffer
1114		configurable. The size of this buffer is also configurable
1115		through the "dfu_bufsiz" environment variable.
1116
1117		CONFIG_SYS_DFU_MAX_FILE_SIZE
1118		When updating files rather than the raw storage device,
1119		we use a static buffer to copy the file into and then write
1120		the buffer once we've been given the whole file.  Define
1121		this to the maximum filesize (in bytes) for the buffer.
1122		Default is 4 MiB if undefined.
1123
1124		DFU_DEFAULT_POLL_TIMEOUT
1125		Poll timeout [ms], is the timeout a device can send to the
1126		host. The host must wait for this timeout before sending
1127		a subsequent DFU_GET_STATUS request to the device.
1128
1129		DFU_MANIFEST_POLL_TIMEOUT
1130		Poll timeout [ms], which the device sends to the host when
1131		entering dfuMANIFEST state. Host waits this timeout, before
1132		sending again an USB request to the device.
1133
1134- Journaling Flash filesystem support:
1135		CONFIG_JFFS2_NAND
1136		Define these for a default partition on a NAND device
1137
1138		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1139		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1140		Define these for a default partition on a NOR device
1141
1142- Keyboard Support:
1143		See Kconfig help for available keyboard drivers.
1144
1145		CONFIG_KEYBOARD
1146
1147		Define this to enable a custom keyboard support.
1148		This simply calls drv_keyboard_init() which must be
1149		defined in your board-specific files. This option is deprecated
1150		and is only used by novena. For new boards, use driver model
1151		instead.
1152
1153- Video support:
1154		CONFIG_FSL_DIU_FB
1155		Enable the Freescale DIU video driver.	Reference boards for
1156		SOCs that have a DIU should define this macro to enable DIU
1157		support, and should also define these other macros:
1158
1159			CONFIG_SYS_DIU_ADDR
1160			CONFIG_VIDEO
1161			CONFIG_CFB_CONSOLE
1162			CONFIG_VIDEO_SW_CURSOR
1163			CONFIG_VGA_AS_SINGLE_DEVICE
1164			CONFIG_VIDEO_LOGO
1165			CONFIG_VIDEO_BMP_LOGO
1166
1167		The DIU driver will look for the 'video-mode' environment
1168		variable, and if defined, enable the DIU as a console during
1169		boot.  See the documentation file doc/README.video for a
1170		description of this variable.
1171
1172- LCD Support:	CONFIG_LCD
1173
1174		Define this to enable LCD support (for output to LCD
1175		display); also select one of the supported displays
1176		by defining one of these:
1177
1178		CONFIG_ATMEL_LCD:
1179
1180			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1181
1182		CONFIG_NEC_NL6448AC33:
1183
1184			NEC NL6448AC33-18. Active, color, single scan.
1185
1186		CONFIG_NEC_NL6448BC20
1187
1188			NEC NL6448BC20-08. 6.5", 640x480.
1189			Active, color, single scan.
1190
1191		CONFIG_NEC_NL6448BC33_54
1192
1193			NEC NL6448BC33-54. 10.4", 640x480.
1194			Active, color, single scan.
1195
1196		CONFIG_SHARP_16x9
1197
1198			Sharp 320x240. Active, color, single scan.
1199			It isn't 16x9, and I am not sure what it is.
1200
1201		CONFIG_SHARP_LQ64D341
1202
1203			Sharp LQ64D341 display, 640x480.
1204			Active, color, single scan.
1205
1206		CONFIG_HLD1045
1207
1208			HLD1045 display, 640x480.
1209			Active, color, single scan.
1210
1211		CONFIG_OPTREX_BW
1212
1213			Optrex	 CBL50840-2 NF-FW 99 22 M5
1214			or
1215			Hitachi	 LMG6912RPFC-00T
1216			or
1217			Hitachi	 SP14Q002
1218
1219			320x240. Black & white.
1220
1221		CONFIG_LCD_ALIGNMENT
1222
1223		Normally the LCD is page-aligned (typically 4KB). If this is
1224		defined then the LCD will be aligned to this value instead.
1225		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1226		here, since it is cheaper to change data cache settings on
1227		a per-section basis.
1228
1229
1230		CONFIG_LCD_ROTATION
1231
1232		Sometimes, for example if the display is mounted in portrait
1233		mode or even if it's mounted landscape but rotated by 180degree,
1234		we need to rotate our content of the display relative to the
1235		framebuffer, so that user can read the messages which are
1236		printed out.
1237		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1238		initialized with a given rotation from "vl_rot" out of
1239		"vidinfo_t" which is provided by the board specific code.
1240		The value for vl_rot is coded as following (matching to
1241		fbcon=rotate:<n> linux-kernel commandline):
1242		0 = no rotation respectively 0 degree
1243		1 = 90 degree rotation
1244		2 = 180 degree rotation
1245		3 = 270 degree rotation
1246
1247		If CONFIG_LCD_ROTATION is not defined, the console will be
1248		initialized with 0degree rotation.
1249
1250		CONFIG_LCD_BMP_RLE8
1251
1252		Support drawing of RLE8-compressed bitmaps on the LCD.
1253
1254		CONFIG_I2C_EDID
1255
1256		Enables an 'i2c edid' command which can read EDID
1257		information over I2C from an attached LCD display.
1258
1259- MII/PHY support:
1260		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1261
1262		The clock frequency of the MII bus
1263
1264		CONFIG_PHY_RESET_DELAY
1265
1266		Some PHY like Intel LXT971A need extra delay after
1267		reset before any MII register access is possible.
1268		For such PHY, set this option to the usec delay
1269		required. (minimum 300usec for LXT971A)
1270
1271		CONFIG_PHY_CMD_DELAY (ppc4xx)
1272
1273		Some PHY like Intel LXT971A need extra delay after
1274		command issued before MII status register can be read
1275
1276- IP address:
1277		CONFIG_IPADDR
1278
1279		Define a default value for the IP address to use for
1280		the default Ethernet interface, in case this is not
1281		determined through e.g. bootp.
1282		(Environment variable "ipaddr")
1283
1284- Server IP address:
1285		CONFIG_SERVERIP
1286
1287		Defines a default value for the IP address of a TFTP
1288		server to contact when using the "tftboot" command.
1289		(Environment variable "serverip")
1290
1291		CONFIG_KEEP_SERVERADDR
1292
1293		Keeps the server's MAC address, in the env 'serveraddr'
1294		for passing to bootargs (like Linux's netconsole option)
1295
1296- Gateway IP address:
1297		CONFIG_GATEWAYIP
1298
1299		Defines a default value for the IP address of the
1300		default router where packets to other networks are
1301		sent to.
1302		(Environment variable "gatewayip")
1303
1304- Subnet mask:
1305		CONFIG_NETMASK
1306
1307		Defines a default value for the subnet mask (or
1308		routing prefix) which is used to determine if an IP
1309		address belongs to the local subnet or needs to be
1310		forwarded through a router.
1311		(Environment variable "netmask")
1312
1313- BOOTP Recovery Mode:
1314		CONFIG_BOOTP_RANDOM_DELAY
1315
1316		If you have many targets in a network that try to
1317		boot using BOOTP, you may want to avoid that all
1318		systems send out BOOTP requests at precisely the same
1319		moment (which would happen for instance at recovery
1320		from a power failure, when all systems will try to
1321		boot, thus flooding the BOOTP server. Defining
1322		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1323		inserted before sending out BOOTP requests. The
1324		following delays are inserted then:
1325
1326		1st BOOTP request:	delay 0 ... 1 sec
1327		2nd BOOTP request:	delay 0 ... 2 sec
1328		3rd BOOTP request:	delay 0 ... 4 sec
1329		4th and following
1330		BOOTP requests:		delay 0 ... 8 sec
1331
1332		CONFIG_BOOTP_ID_CACHE_SIZE
1333
1334		BOOTP packets are uniquely identified using a 32-bit ID. The
1335		server will copy the ID from client requests to responses and
1336		U-Boot will use this to determine if it is the destination of
1337		an incoming response. Some servers will check that addresses
1338		aren't in use before handing them out (usually using an ARP
1339		ping) and therefore take up to a few hundred milliseconds to
1340		respond. Network congestion may also influence the time it
1341		takes for a response to make it back to the client. If that
1342		time is too long, U-Boot will retransmit requests. In order
1343		to allow earlier responses to still be accepted after these
1344		retransmissions, U-Boot's BOOTP client keeps a small cache of
1345		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1346		cache. The default is to keep IDs for up to four outstanding
1347		requests. Increasing this will allow U-Boot to accept offers
1348		from a BOOTP client in networks with unusually high latency.
1349
1350- DHCP Advanced Options:
1351		You can fine tune the DHCP functionality by defining
1352		CONFIG_BOOTP_* symbols:
1353
1354		CONFIG_BOOTP_NISDOMAIN
1355		CONFIG_BOOTP_BOOTFILESIZE
1356		CONFIG_BOOTP_NTPSERVER
1357		CONFIG_BOOTP_TIMEOFFSET
1358		CONFIG_BOOTP_VENDOREX
1359		CONFIG_BOOTP_MAY_FAIL
1360
1361		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1362		environment variable, not the BOOTP server.
1363
1364		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1365		after the configured retry count, the call will fail
1366		instead of starting over.  This can be used to fail over
1367		to Link-local IP address configuration if the DHCP server
1368		is not available.
1369
1370		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1371
1372		A 32bit value in microseconds for a delay between
1373		receiving a "DHCP Offer" and sending the "DHCP Request".
1374		This fixes a problem with certain DHCP servers that don't
1375		respond 100% of the time to a "DHCP request". E.g. On an
1376		AT91RM9200 processor running at 180MHz, this delay needed
1377		to be *at least* 15,000 usec before a Windows Server 2003
1378		DHCP server would reply 100% of the time. I recommend at
1379		least 50,000 usec to be safe. The alternative is to hope
1380		that one of the retries will be successful but note that
1381		the DHCP timeout and retry process takes a longer than
1382		this delay.
1383
1384 - Link-local IP address negotiation:
1385		Negotiate with other link-local clients on the local network
1386		for an address that doesn't require explicit configuration.
1387		This is especially useful if a DHCP server cannot be guaranteed
1388		to exist in all environments that the device must operate.
1389
1390		See doc/README.link-local for more information.
1391
1392 - MAC address from environment variables
1393
1394		FDT_SEQ_MACADDR_FROM_ENV
1395
1396		Fix-up device tree with MAC addresses fetched sequentially from
1397		environment variables. This config work on assumption that
1398		non-usable ethernet node of device-tree are either not present
1399		or their status has been marked as "disabled".
1400
1401 - CDP Options:
1402		CONFIG_CDP_DEVICE_ID
1403
1404		The device id used in CDP trigger frames.
1405
1406		CONFIG_CDP_DEVICE_ID_PREFIX
1407
1408		A two character string which is prefixed to the MAC address
1409		of the device.
1410
1411		CONFIG_CDP_PORT_ID
1412
1413		A printf format string which contains the ascii name of
1414		the port. Normally is set to "eth%d" which sets
1415		eth0 for the first Ethernet, eth1 for the second etc.
1416
1417		CONFIG_CDP_CAPABILITIES
1418
1419		A 32bit integer which indicates the device capabilities;
1420		0x00000010 for a normal host which does not forwards.
1421
1422		CONFIG_CDP_VERSION
1423
1424		An ascii string containing the version of the software.
1425
1426		CONFIG_CDP_PLATFORM
1427
1428		An ascii string containing the name of the platform.
1429
1430		CONFIG_CDP_TRIGGER
1431
1432		A 32bit integer sent on the trigger.
1433
1434		CONFIG_CDP_POWER_CONSUMPTION
1435
1436		A 16bit integer containing the power consumption of the
1437		device in .1 of milliwatts.
1438
1439		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1440
1441		A byte containing the id of the VLAN.
1442
1443- Status LED:	CONFIG_LED_STATUS
1444
1445		Several configurations allow to display the current
1446		status using a LED. For instance, the LED will blink
1447		fast while running U-Boot code, stop blinking as
1448		soon as a reply to a BOOTP request was received, and
1449		start blinking slow once the Linux kernel is running
1450		(supported by a status LED driver in the Linux
1451		kernel). Defining CONFIG_LED_STATUS enables this
1452		feature in U-Boot.
1453
1454		Additional options:
1455
1456		CONFIG_LED_STATUS_GPIO
1457		The status LED can be connected to a GPIO pin.
1458		In such cases, the gpio_led driver can be used as a
1459		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1460		to include the gpio_led driver in the U-Boot binary.
1461
1462		CONFIG_GPIO_LED_INVERTED_TABLE
1463		Some GPIO connected LEDs may have inverted polarity in which
1464		case the GPIO high value corresponds to LED off state and
1465		GPIO low value corresponds to LED on state.
1466		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1467		with a list of GPIO LEDs that have inverted polarity.
1468
1469- I2C Support:	CONFIG_SYS_I2C
1470
1471		This enable the NEW i2c subsystem, and will allow you to use
1472		i2c commands at the u-boot command line (as long as you set
1473		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1474		    for defining speed and slave address
1475		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1476		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1477		    for defining speed and slave address
1478		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1479		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1480		    for defining speed and slave address
1481		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1482		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1483		    for defining speed and slave address
1484
1485		- drivers/i2c/fsl_i2c.c:
1486		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1487		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1488		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1489		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1490		    bus.
1491		  - If your board supports a second fsl i2c bus, define
1492		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1493		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1494		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1495		    second bus.
1496
1497		- drivers/i2c/tegra_i2c.c:
1498		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1499		  - This driver adds 4 i2c buses with a fix speed from
1500		    100000 and the slave addr 0!
1501
1502		- drivers/i2c/ppc4xx_i2c.c
1503		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1504		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1505		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1506
1507		- drivers/i2c/i2c_mxc.c
1508		  - activate this driver with CONFIG_SYS_I2C_MXC
1509		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1510		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1511		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1512		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1513		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1514		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1515		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1516		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1517		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1518		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1519		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1520		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1521		If those defines are not set, default value is 100000
1522		for speed, and 0 for slave.
1523
1524		- drivers/i2c/rcar_i2c.c:
1525		  - activate this driver with CONFIG_SYS_I2C_RCAR
1526		  - This driver adds 4 i2c buses
1527
1528		- drivers/i2c/sh_i2c.c:
1529		  - activate this driver with CONFIG_SYS_I2C_SH
1530		  - This driver adds from 2 to 5 i2c buses
1531
1532		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1533		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1534		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1535		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1536		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1537		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1538		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1539		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1540		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1541		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1542		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1543
1544		- drivers/i2c/omap24xx_i2c.c
1545		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1546		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1547		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1548		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1549		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1550		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1551		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1552		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1553		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1554		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1555		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1556
1557		- drivers/i2c/s3c24x0_i2c.c:
1558		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1559		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1560		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1561		    with a fix speed from 100000 and the slave addr 0!
1562
1563		- drivers/i2c/ihs_i2c.c
1564		  - activate this driver with CONFIG_SYS_I2C_IHS
1565		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1566		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1567		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1568		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1569		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1570		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1571		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1572		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1573		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1574		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1575		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1576		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1577		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1578		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1579		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1580		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1581		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1582		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1583		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1584		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1585		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1586
1587		additional defines:
1588
1589		CONFIG_SYS_NUM_I2C_BUSES
1590		Hold the number of i2c buses you want to use.
1591
1592		CONFIG_SYS_I2C_DIRECT_BUS
1593		define this, if you don't use i2c muxes on your hardware.
1594		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1595		omit this define.
1596
1597		CONFIG_SYS_I2C_MAX_HOPS
1598		define how many muxes are maximal consecutively connected
1599		on one i2c bus. If you not use i2c muxes, omit this
1600		define.
1601
1602		CONFIG_SYS_I2C_BUSES
1603		hold a list of buses you want to use, only used if
1604		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1605		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1606		CONFIG_SYS_NUM_I2C_BUSES = 9:
1607
1608		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1609					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1610					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1611					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1612					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1613					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1614					{1, {I2C_NULL_HOP}}, \
1615					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1616					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1617					}
1618
1619		which defines
1620			bus 0 on adapter 0 without a mux
1621			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1622			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1623			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1624			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1625			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1626			bus 6 on adapter 1 without a mux
1627			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1628			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1629
1630		If you do not have i2c muxes on your board, omit this define.
1631
1632- Legacy I2C Support:
1633		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1634		then the following macros need to be defined (examples are
1635		from include/configs/lwmon.h):
1636
1637		I2C_INIT
1638
1639		(Optional). Any commands necessary to enable the I2C
1640		controller or configure ports.
1641
1642		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1643
1644		I2C_ACTIVE
1645
1646		The code necessary to make the I2C data line active
1647		(driven).  If the data line is open collector, this
1648		define can be null.
1649
1650		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1651
1652		I2C_TRISTATE
1653
1654		The code necessary to make the I2C data line tri-stated
1655		(inactive).  If the data line is open collector, this
1656		define can be null.
1657
1658		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1659
1660		I2C_READ
1661
1662		Code that returns true if the I2C data line is high,
1663		false if it is low.
1664
1665		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1666
1667		I2C_SDA(bit)
1668
1669		If <bit> is true, sets the I2C data line high. If it
1670		is false, it clears it (low).
1671
1672		eg: #define I2C_SDA(bit) \
1673			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1674			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1675
1676		I2C_SCL(bit)
1677
1678		If <bit> is true, sets the I2C clock line high. If it
1679		is false, it clears it (low).
1680
1681		eg: #define I2C_SCL(bit) \
1682			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1683			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1684
1685		I2C_DELAY
1686
1687		This delay is invoked four times per clock cycle so this
1688		controls the rate of data transfer.  The data rate thus
1689		is 1 / (I2C_DELAY * 4). Often defined to be something
1690		like:
1691
1692		#define I2C_DELAY  udelay(2)
1693
1694		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1695
1696		If your arch supports the generic GPIO framework (asm/gpio.h),
1697		then you may alternatively define the two GPIOs that are to be
1698		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1699		have GPIO-based defaults assigned to them as appropriate.
1700
1701		You should define these to the GPIO value as given directly to
1702		the generic GPIO functions.
1703
1704		CONFIG_SYS_I2C_INIT_BOARD
1705
1706		When a board is reset during an i2c bus transfer
1707		chips might think that the current transfer is still
1708		in progress. On some boards it is possible to access
1709		the i2c SCLK line directly, either by using the
1710		processor pin as a GPIO or by having a second pin
1711		connected to the bus. If this option is defined a
1712		custom i2c_init_board() routine in boards/xxx/board.c
1713		is run early in the boot sequence.
1714
1715		CONFIG_I2C_MULTI_BUS
1716
1717		This option allows the use of multiple I2C buses, each of which
1718		must have a controller.	 At any point in time, only one bus is
1719		active.	 To switch to a different bus, use the 'i2c dev' command.
1720		Note that bus numbering is zero-based.
1721
1722		CONFIG_SYS_I2C_NOPROBES
1723
1724		This option specifies a list of I2C devices that will be skipped
1725		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1726		is set, specify a list of bus-device pairs.  Otherwise, specify
1727		a 1D array of device addresses
1728
1729		e.g.
1730			#undef	CONFIG_I2C_MULTI_BUS
1731			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1732
1733		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1734
1735			#define CONFIG_I2C_MULTI_BUS
1736			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1737
1738		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1739
1740		CONFIG_SYS_SPD_BUS_NUM
1741
1742		If defined, then this indicates the I2C bus number for DDR SPD.
1743		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1744
1745		CONFIG_SYS_RTC_BUS_NUM
1746
1747		If defined, then this indicates the I2C bus number for the RTC.
1748		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1749
1750		CONFIG_SOFT_I2C_READ_REPEATED_START
1751
1752		defining this will force the i2c_read() function in
1753		the soft_i2c driver to perform an I2C repeated start
1754		between writing the address pointer and reading the
1755		data.  If this define is omitted the default behaviour
1756		of doing a stop-start sequence will be used.  Most I2C
1757		devices can use either method, but some require one or
1758		the other.
1759
1760- SPI Support:	CONFIG_SPI
1761
1762		Enables SPI driver (so far only tested with
1763		SPI EEPROM, also an instance works with Crystal A/D and
1764		D/As on the SACSng board)
1765
1766		CONFIG_SOFT_SPI
1767
1768		Enables a software (bit-bang) SPI driver rather than
1769		using hardware support. This is a general purpose
1770		driver that only requires three general I/O port pins
1771		(two outputs, one input) to function. If this is
1772		defined, the board configuration must define several
1773		SPI configuration items (port pins to use, etc). For
1774		an example, see include/configs/sacsng.h.
1775
1776		CONFIG_SYS_SPI_MXC_WAIT
1777		Timeout for waiting until spi transfer completed.
1778		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1779
1780- FPGA Support: CONFIG_FPGA
1781
1782		Enables FPGA subsystem.
1783
1784		CONFIG_FPGA_<vendor>
1785
1786		Enables support for specific chip vendors.
1787		(ALTERA, XILINX)
1788
1789		CONFIG_FPGA_<family>
1790
1791		Enables support for FPGA family.
1792		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1793
1794		CONFIG_FPGA_COUNT
1795
1796		Specify the number of FPGA devices to support.
1797
1798		CONFIG_SYS_FPGA_PROG_FEEDBACK
1799
1800		Enable printing of hash marks during FPGA configuration.
1801
1802		CONFIG_SYS_FPGA_CHECK_BUSY
1803
1804		Enable checks on FPGA configuration interface busy
1805		status by the configuration function. This option
1806		will require a board or device specific function to
1807		be written.
1808
1809		CONFIG_FPGA_DELAY
1810
1811		If defined, a function that provides delays in the FPGA
1812		configuration driver.
1813
1814		CONFIG_SYS_FPGA_CHECK_CTRLC
1815		Allow Control-C to interrupt FPGA configuration
1816
1817		CONFIG_SYS_FPGA_CHECK_ERROR
1818
1819		Check for configuration errors during FPGA bitfile
1820		loading. For example, abort during Virtex II
1821		configuration if the INIT_B line goes low (which
1822		indicated a CRC error).
1823
1824		CONFIG_SYS_FPGA_WAIT_INIT
1825
1826		Maximum time to wait for the INIT_B line to de-assert
1827		after PROB_B has been de-asserted during a Virtex II
1828		FPGA configuration sequence. The default time is 500
1829		ms.
1830
1831		CONFIG_SYS_FPGA_WAIT_BUSY
1832
1833		Maximum time to wait for BUSY to de-assert during
1834		Virtex II FPGA configuration. The default is 5 ms.
1835
1836		CONFIG_SYS_FPGA_WAIT_CONFIG
1837
1838		Time to wait after FPGA configuration. The default is
1839		200 ms.
1840
1841- Configuration Management:
1842
1843		CONFIG_IDENT_STRING
1844
1845		If defined, this string will be added to the U-Boot
1846		version information (U_BOOT_VERSION)
1847
1848- Vendor Parameter Protection:
1849
1850		U-Boot considers the values of the environment
1851		variables "serial#" (Board Serial Number) and
1852		"ethaddr" (Ethernet Address) to be parameters that
1853		are set once by the board vendor / manufacturer, and
1854		protects these variables from casual modification by
1855		the user. Once set, these variables are read-only,
1856		and write or delete attempts are rejected. You can
1857		change this behaviour:
1858
1859		If CONFIG_ENV_OVERWRITE is #defined in your config
1860		file, the write protection for vendor parameters is
1861		completely disabled. Anybody can change or delete
1862		these parameters.
1863
1864		Alternatively, if you define _both_ an ethaddr in the
1865		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1866		Ethernet address is installed in the environment,
1867		which can be changed exactly ONCE by the user. [The
1868		serial# is unaffected by this, i. e. it remains
1869		read-only.]
1870
1871		The same can be accomplished in a more flexible way
1872		for any variable by configuring the type of access
1873		to allow for those variables in the ".flags" variable
1874		or define CONFIG_ENV_FLAGS_LIST_STATIC.
1875
1876- Protected RAM:
1877		CONFIG_PRAM
1878
1879		Define this variable to enable the reservation of
1880		"protected RAM", i. e. RAM which is not overwritten
1881		by U-Boot. Define CONFIG_PRAM to hold the number of
1882		kB you want to reserve for pRAM. You can overwrite
1883		this default value by defining an environment
1884		variable "pram" to the number of kB you want to
1885		reserve. Note that the board info structure will
1886		still show the full amount of RAM. If pRAM is
1887		reserved, a new environment variable "mem" will
1888		automatically be defined to hold the amount of
1889		remaining RAM in a form that can be passed as boot
1890		argument to Linux, for instance like that:
1891
1892			setenv bootargs ... mem=\${mem}
1893			saveenv
1894
1895		This way you can tell Linux not to use this memory,
1896		either, which results in a memory region that will
1897		not be affected by reboots.
1898
1899		*WARNING* If your board configuration uses automatic
1900		detection of the RAM size, you must make sure that
1901		this memory test is non-destructive. So far, the
1902		following board configurations are known to be
1903		"pRAM-clean":
1904
1905			IVMS8, IVML24, SPD8xx,
1906			HERMES, IP860, RPXlite, LWMON,
1907			FLAGADM
1908
1909- Access to physical memory region (> 4GB)
1910		Some basic support is provided for operations on memory not
1911		normally accessible to U-Boot - e.g. some architectures
1912		support access to more than 4GB of memory on 32-bit
1913		machines using physical address extension or similar.
1914		Define CONFIG_PHYSMEM to access this basic support, which
1915		currently only supports clearing the memory.
1916
1917- Error Recovery:
1918		CONFIG_NET_RETRY_COUNT
1919
1920		This variable defines the number of retries for
1921		network operations like ARP, RARP, TFTP, or BOOTP
1922		before giving up the operation. If not defined, a
1923		default value of 5 is used.
1924
1925		CONFIG_ARP_TIMEOUT
1926
1927		Timeout waiting for an ARP reply in milliseconds.
1928
1929		CONFIG_NFS_TIMEOUT
1930
1931		Timeout in milliseconds used in NFS protocol.
1932		If you encounter "ERROR: Cannot umount" in nfs command,
1933		try longer timeout such as
1934		#define CONFIG_NFS_TIMEOUT 10000UL
1935
1936	Note:
1937
1938		In the current implementation, the local variables
1939		space and global environment variables space are
1940		separated. Local variables are those you define by
1941		simply typing `name=value'. To access a local
1942		variable later on, you have write `$name' or
1943		`${name}'; to execute the contents of a variable
1944		directly type `$name' at the command prompt.
1945
1946		Global environment variables are those you use
1947		setenv/printenv to work with. To run a command stored
1948		in such a variable, you need to use the run command,
1949		and you must not use the '$' sign to access them.
1950
1951		To store commands and special characters in a
1952		variable, please use double quotation marks
1953		surrounding the whole text of the variable, instead
1954		of the backslashes before semicolons and special
1955		symbols.
1956
1957- Command Line Editing and History:
1958		CONFIG_CMDLINE_PS_SUPPORT
1959
1960		Enable support for changing the command prompt string
1961		at run-time. Only static string is supported so far.
1962		The string is obtained from environment variables PS1
1963		and PS2.
1964
1965- Default Environment:
1966		CONFIG_EXTRA_ENV_SETTINGS
1967
1968		Define this to contain any number of null terminated
1969		strings (variable = value pairs) that will be part of
1970		the default environment compiled into the boot image.
1971
1972		For example, place something like this in your
1973		board's config file:
1974
1975		#define CONFIG_EXTRA_ENV_SETTINGS \
1976			"myvar1=value1\0" \
1977			"myvar2=value2\0"
1978
1979		Warning: This method is based on knowledge about the
1980		internal format how the environment is stored by the
1981		U-Boot code. This is NOT an official, exported
1982		interface! Although it is unlikely that this format
1983		will change soon, there is no guarantee either.
1984		You better know what you are doing here.
1985
1986		Note: overly (ab)use of the default environment is
1987		discouraged. Make sure to check other ways to preset
1988		the environment like the "source" command or the
1989		boot command first.
1990
1991		CONFIG_DELAY_ENVIRONMENT
1992
1993		Normally the environment is loaded when the board is
1994		initialised so that it is available to U-Boot. This inhibits
1995		that so that the environment is not available until
1996		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1997		this is instead controlled by the value of
1998		/config/load-environment.
1999
2000- TFTP Fixed UDP Port:
2001		CONFIG_TFTP_PORT
2002
2003		If this is defined, the environment variable tftpsrcp
2004		is used to supply the TFTP UDP source port value.
2005		If tftpsrcp isn't defined, the normal pseudo-random port
2006		number generator is used.
2007
2008		Also, the environment variable tftpdstp is used to supply
2009		the TFTP UDP destination port value.  If tftpdstp isn't
2010		defined, the normal port 69 is used.
2011
2012		The purpose for tftpsrcp is to allow a TFTP server to
2013		blindly start the TFTP transfer using the pre-configured
2014		target IP address and UDP port. This has the effect of
2015		"punching through" the (Windows XP) firewall, allowing
2016		the remainder of the TFTP transfer to proceed normally.
2017		A better solution is to properly configure the firewall,
2018		but sometimes that is not allowed.
2019
2020		CONFIG_STANDALONE_LOAD_ADDR
2021
2022		This option defines a board specific value for the
2023		address where standalone program gets loaded, thus
2024		overwriting the architecture dependent default
2025		settings.
2026
2027- Frame Buffer Address:
2028		CONFIG_FB_ADDR
2029
2030		Define CONFIG_FB_ADDR if you want to use specific
2031		address for frame buffer.  This is typically the case
2032		when using a graphics controller has separate video
2033		memory.  U-Boot will then place the frame buffer at
2034		the given address instead of dynamically reserving it
2035		in system RAM by calling lcd_setmem(), which grabs
2036		the memory for the frame buffer depending on the
2037		configured panel size.
2038
2039		Please see board_init_f function.
2040
2041- Automatic software updates via TFTP server
2042		CONFIG_UPDATE_TFTP
2043		CONFIG_UPDATE_TFTP_CNT_MAX
2044		CONFIG_UPDATE_TFTP_MSEC_MAX
2045
2046		These options enable and control the auto-update feature;
2047		for a more detailed description refer to doc/README.update.
2048
2049- MTD Support (mtdparts command, UBI support)
2050		CONFIG_MTD_UBI_WL_THRESHOLD
2051		This parameter defines the maximum difference between the highest
2052		erase counter value and the lowest erase counter value of eraseblocks
2053		of UBI devices. When this threshold is exceeded, UBI starts performing
2054		wear leveling by means of moving data from eraseblock with low erase
2055		counter to eraseblocks with high erase counter.
2056
2057		The default value should be OK for SLC NAND flashes, NOR flashes and
2058		other flashes which have eraseblock life-cycle 100000 or more.
2059		However, in case of MLC NAND flashes which typically have eraseblock
2060		life-cycle less than 10000, the threshold should be lessened (e.g.,
2061		to 128 or 256, although it does not have to be power of 2).
2062
2063		default: 4096
2064
2065		CONFIG_MTD_UBI_BEB_LIMIT
2066		This option specifies the maximum bad physical eraseblocks UBI
2067		expects on the MTD device (per 1024 eraseblocks). If the
2068		underlying flash does not admit of bad eraseblocks (e.g. NOR
2069		flash), this value is ignored.
2070
2071		NAND datasheets often specify the minimum and maximum NVM
2072		(Number of Valid Blocks) for the flashes' endurance lifetime.
2073		The maximum expected bad eraseblocks per 1024 eraseblocks
2074		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2075		which gives 20 for most NANDs (MaxNVB is basically the total
2076		count of eraseblocks on the chip).
2077
2078		To put it differently, if this value is 20, UBI will try to
2079		reserve about 1.9% of physical eraseblocks for bad blocks
2080		handling. And that will be 1.9% of eraseblocks on the entire
2081		NAND chip, not just the MTD partition UBI attaches. This means
2082		that if you have, say, a NAND flash chip admits maximum 40 bad
2083		eraseblocks, and it is split on two MTD partitions of the same
2084		size, UBI will reserve 40 eraseblocks when attaching a
2085		partition.
2086
2087		default: 20
2088
2089		CONFIG_MTD_UBI_FASTMAP
2090		Fastmap is a mechanism which allows attaching an UBI device
2091		in nearly constant time. Instead of scanning the whole MTD device it
2092		only has to locate a checkpoint (called fastmap) on the device.
2093		The on-flash fastmap contains all information needed to attach
2094		the device. Using fastmap makes only sense on large devices where
2095		attaching by scanning takes long. UBI will not automatically install
2096		a fastmap on old images, but you can set the UBI parameter
2097		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2098		that fastmap-enabled images are still usable with UBI implementations
2099		without	fastmap support. On typical flash devices the whole fastmap
2100		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2101
2102		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2103		Set this parameter to enable fastmap automatically on images
2104		without a fastmap.
2105		default: 0
2106
2107		CONFIG_MTD_UBI_FM_DEBUG
2108		Enable UBI fastmap debug
2109		default: 0
2110
2111- SPL framework
2112		CONFIG_SPL
2113		Enable building of SPL globally.
2114
2115		CONFIG_SPL_LDSCRIPT
2116		LDSCRIPT for linking the SPL binary.
2117
2118		CONFIG_SPL_MAX_FOOTPRINT
2119		Maximum size in memory allocated to the SPL, BSS included.
2120		When defined, the linker checks that the actual memory
2121		used by SPL from _start to __bss_end does not exceed it.
2122		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2123		must not be both defined at the same time.
2124
2125		CONFIG_SPL_MAX_SIZE
2126		Maximum size of the SPL image (text, data, rodata, and
2127		linker lists sections), BSS excluded.
2128		When defined, the linker checks that the actual size does
2129		not exceed it.
2130
2131		CONFIG_SPL_RELOC_TEXT_BASE
2132		Address to relocate to.  If unspecified, this is equal to
2133		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2134
2135		CONFIG_SPL_BSS_START_ADDR
2136		Link address for the BSS within the SPL binary.
2137
2138		CONFIG_SPL_BSS_MAX_SIZE
2139		Maximum size in memory allocated to the SPL BSS.
2140		When defined, the linker checks that the actual memory used
2141		by SPL from __bss_start to __bss_end does not exceed it.
2142		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2143		must not be both defined at the same time.
2144
2145		CONFIG_SPL_STACK
2146		Adress of the start of the stack SPL will use
2147
2148		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2149		When defined, SPL will panic() if the image it has
2150		loaded does not have a signature.
2151		Defining this is useful when code which loads images
2152		in SPL cannot guarantee that absolutely all read errors
2153		will be caught.
2154		An example is the LPC32XX MLC NAND driver, which will
2155		consider that a completely unreadable NAND block is bad,
2156		and thus should be skipped silently.
2157
2158		CONFIG_SPL_RELOC_STACK
2159		Adress of the start of the stack SPL will use after
2160		relocation.  If unspecified, this is equal to
2161		CONFIG_SPL_STACK.
2162
2163		CONFIG_SYS_SPL_MALLOC_START
2164		Starting address of the malloc pool used in SPL.
2165		When this option is set the full malloc is used in SPL and
2166		it is set up by spl_init() and before that, the simple malloc()
2167		can be used if CONFIG_SYS_MALLOC_F is defined.
2168
2169		CONFIG_SYS_SPL_MALLOC_SIZE
2170		The size of the malloc pool used in SPL.
2171
2172		CONFIG_SPL_OS_BOOT
2173		Enable booting directly to an OS from SPL.
2174		See also: doc/README.falcon
2175
2176		CONFIG_SPL_DISPLAY_PRINT
2177		For ARM, enable an optional function to print more information
2178		about the running system.
2179
2180		CONFIG_SPL_INIT_MINIMAL
2181		Arch init code should be built for a very small image
2182
2183		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2184		Partition on the MMC to load U-Boot from when the MMC is being
2185		used in raw mode
2186
2187		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2188		Sector to load kernel uImage from when MMC is being
2189		used in raw mode (for Falcon mode)
2190
2191		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2192		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2193		Sector and number of sectors to load kernel argument
2194		parameters from when MMC is being used in raw mode
2195		(for falcon mode)
2196
2197		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2198		Filename to read to load U-Boot when reading from filesystem
2199
2200		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2201		Filename to read to load kernel uImage when reading
2202		from filesystem (for Falcon mode)
2203
2204		CONFIG_SPL_FS_LOAD_ARGS_NAME
2205		Filename to read to load kernel argument parameters
2206		when reading from filesystem (for Falcon mode)
2207
2208		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2209		Set this for NAND SPL on PPC mpc83xx targets, so that
2210		start.S waits for the rest of the SPL to load before
2211		continuing (the hardware starts execution after just
2212		loading the first page rather than the full 4K).
2213
2214		CONFIG_SPL_SKIP_RELOCATE
2215		Avoid SPL relocation
2216
2217		CONFIG_SPL_NAND_IDENT
2218		SPL uses the chip ID list to identify the NAND flash.
2219		Requires CONFIG_SPL_NAND_BASE.
2220
2221		CONFIG_SPL_UBI
2222		Support for a lightweight UBI (fastmap) scanner and
2223		loader
2224
2225		CONFIG_SPL_NAND_RAW_ONLY
2226		Support to boot only raw u-boot.bin images. Use this only
2227		if you need to save space.
2228
2229		CONFIG_SPL_COMMON_INIT_DDR
2230		Set for common ddr init with serial presence detect in
2231		SPL binary.
2232
2233		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2234		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2235		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2236		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2237		CONFIG_SYS_NAND_ECCBYTES
2238		Defines the size and behavior of the NAND that SPL uses
2239		to read U-Boot
2240
2241		CONFIG_SYS_NAND_U_BOOT_OFFS
2242		Location in NAND to read U-Boot from
2243
2244		CONFIG_SYS_NAND_U_BOOT_DST
2245		Location in memory to load U-Boot to
2246
2247		CONFIG_SYS_NAND_U_BOOT_SIZE
2248		Size of image to load
2249
2250		CONFIG_SYS_NAND_U_BOOT_START
2251		Entry point in loaded image to jump to
2252
2253		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2254		Define this if you need to first read the OOB and then the
2255		data. This is used, for example, on davinci platforms.
2256
2257		CONFIG_SPL_RAM_DEVICE
2258		Support for running image already present in ram, in SPL binary
2259
2260		CONFIG_SPL_PAD_TO
2261		Image offset to which the SPL should be padded before appending
2262		the SPL payload. By default, this is defined as
2263		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2264		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2265		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2266
2267		CONFIG_SPL_TARGET
2268		Final target image containing SPL and payload.  Some SPLs
2269		use an arch-specific makefile fragment instead, for
2270		example if more than one image needs to be produced.
2271
2272		CONFIG_SPL_FIT_PRINT
2273		Printing information about a FIT image adds quite a bit of
2274		code to SPL. So this is normally disabled in SPL. Use this
2275		option to re-enable it. This will affect the output of the
2276		bootm command when booting a FIT image.
2277
2278- TPL framework
2279		CONFIG_TPL
2280		Enable building of TPL globally.
2281
2282		CONFIG_TPL_PAD_TO
2283		Image offset to which the TPL should be padded before appending
2284		the TPL payload. By default, this is defined as
2285		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2286		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2287		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2288
2289- Interrupt support (PPC):
2290
2291		There are common interrupt_init() and timer_interrupt()
2292		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2293		for CPU specific initialization. interrupt_init_cpu()
2294		should set decrementer_count to appropriate value. If
2295		CPU resets decrementer automatically after interrupt
2296		(ppc4xx) it should set decrementer_count to zero.
2297		timer_interrupt() calls timer_interrupt_cpu() for CPU
2298		specific handling. If board has watchdog / status_led
2299		/ other_activity_monitor it works automatically from
2300		general timer_interrupt().
2301
2302
2303Board initialization settings:
2304------------------------------
2305
2306During Initialization u-boot calls a number of board specific functions
2307to allow the preparation of board specific prerequisites, e.g. pin setup
2308before drivers are initialized. To enable these callbacks the
2309following configuration macros have to be defined. Currently this is
2310architecture specific, so please check arch/your_architecture/lib/board.c
2311typically in board_init_f() and board_init_r().
2312
2313- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2314- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2315- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2316- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2317
2318Configuration Settings:
2319-----------------------
2320
2321- MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2322		Optionally it can be defined to support 64-bit memory commands.
2323
2324- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2325		undefine this when you're short of memory.
2326
2327- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2328		width of the commands listed in the 'help' command output.
2329
2330- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2331		prompt for user input.
2332
2333- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2334
2335- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2336
2337- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2338
2339- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2340		the application (usually a Linux kernel) when it is
2341		booted
2342
2343- CONFIG_SYS_BAUDRATE_TABLE:
2344		List of legal baudrate settings for this board.
2345
2346- CONFIG_SYS_MEM_RESERVE_SECURE
2347		Only implemented for ARMv8 for now.
2348		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2349		is substracted from total RAM and won't be reported to OS.
2350		This memory can be used as secure memory. A variable
2351		gd->arch.secure_ram is used to track the location. In systems
2352		the RAM base is not zero, or RAM is divided into banks,
2353		this variable needs to be recalcuated to get the address.
2354
2355- CONFIG_SYS_MEM_TOP_HIDE:
2356		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2357		this specified memory area will get subtracted from the top
2358		(end) of RAM and won't get "touched" at all by U-Boot. By
2359		fixing up gd->ram_size the Linux kernel should gets passed
2360		the now "corrected" memory size and won't touch it either.
2361		This should work for arch/ppc and arch/powerpc. Only Linux
2362		board ports in arch/powerpc with bootwrapper support that
2363		recalculate the memory size from the SDRAM controller setup
2364		will have to get fixed in Linux additionally.
2365
2366		This option can be used as a workaround for the 440EPx/GRx
2367		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2368		be touched.
2369
2370		WARNING: Please make sure that this value is a multiple of
2371		the Linux page size (normally 4k). If this is not the case,
2372		then the end address of the Linux memory will be located at a
2373		non page size aligned address and this could cause major
2374		problems.
2375
2376- CONFIG_SYS_LOADS_BAUD_CHANGE:
2377		Enable temporary baudrate change while serial download
2378
2379- CONFIG_SYS_SDRAM_BASE:
2380		Physical start address of SDRAM. _Must_ be 0 here.
2381
2382- CONFIG_SYS_FLASH_BASE:
2383		Physical start address of Flash memory.
2384
2385- CONFIG_SYS_MONITOR_BASE:
2386		Physical start address of boot monitor code (set by
2387		make config files to be same as the text base address
2388		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2389		CONFIG_SYS_FLASH_BASE when booting from flash.
2390
2391- CONFIG_SYS_MONITOR_LEN:
2392		Size of memory reserved for monitor code, used to
2393		determine _at_compile_time_ (!) if the environment is
2394		embedded within the U-Boot image, or in a separate
2395		flash sector.
2396
2397- CONFIG_SYS_MALLOC_LEN:
2398		Size of DRAM reserved for malloc() use.
2399
2400- CONFIG_SYS_MALLOC_F_LEN
2401		Size of the malloc() pool for use before relocation. If
2402		this is defined, then a very simple malloc() implementation
2403		will become available before relocation. The address is just
2404		below the global data, and the stack is moved down to make
2405		space.
2406
2407		This feature allocates regions with increasing addresses
2408		within the region. calloc() is supported, but realloc()
2409		is not available. free() is supported but does nothing.
2410		The memory will be freed (or in fact just forgotten) when
2411		U-Boot relocates itself.
2412
2413- CONFIG_SYS_MALLOC_SIMPLE
2414		Provides a simple and small malloc() and calloc() for those
2415		boards which do not use the full malloc in SPL (which is
2416		enabled with CONFIG_SYS_SPL_MALLOC_START).
2417
2418- CONFIG_SYS_NONCACHED_MEMORY:
2419		Size of non-cached memory area. This area of memory will be
2420		typically located right below the malloc() area and mapped
2421		uncached in the MMU. This is useful for drivers that would
2422		otherwise require a lot of explicit cache maintenance. For
2423		some drivers it's also impossible to properly maintain the
2424		cache. For example if the regions that need to be flushed
2425		are not a multiple of the cache-line size, *and* padding
2426		cannot be allocated between the regions to align them (i.e.
2427		if the HW requires a contiguous array of regions, and the
2428		size of each region is not cache-aligned), then a flush of
2429		one region may result in overwriting data that hardware has
2430		written to another region in the same cache-line. This can
2431		happen for example in network drivers where descriptors for
2432		buffers are typically smaller than the CPU cache-line (e.g.
2433		16 bytes vs. 32 or 64 bytes).
2434
2435		Non-cached memory is only supported on 32-bit ARM at present.
2436
2437- CONFIG_SYS_BOOTM_LEN:
2438		Normally compressed uImages are limited to an
2439		uncompressed size of 8 MBytes. If this is not enough,
2440		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2441		to adjust this setting to your needs.
2442
2443- CONFIG_SYS_BOOTMAPSZ:
2444		Maximum size of memory mapped by the startup code of
2445		the Linux kernel; all data that must be processed by
2446		the Linux kernel (bd_info, boot arguments, FDT blob if
2447		used) must be put below this limit, unless "bootm_low"
2448		environment variable is defined and non-zero. In such case
2449		all data for the Linux kernel must be between "bootm_low"
2450		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2451		variable "bootm_mapsize" will override the value of
2452		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2453		then the value in "bootm_size" will be used instead.
2454
2455- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2456		Enable initrd_high functionality.  If defined then the
2457		initrd_high feature is enabled and the bootm ramdisk subcommand
2458		is enabled.
2459
2460- CONFIG_SYS_BOOT_GET_CMDLINE:
2461		Enables allocating and saving kernel cmdline in space between
2462		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2463
2464- CONFIG_SYS_BOOT_GET_KBD:
2465		Enables allocating and saving a kernel copy of the bd_info in
2466		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2467
2468- CONFIG_SYS_MAX_FLASH_BANKS:
2469		Max number of Flash memory banks
2470
2471- CONFIG_SYS_MAX_FLASH_SECT:
2472		Max number of sectors on a Flash chip
2473
2474- CONFIG_SYS_FLASH_ERASE_TOUT:
2475		Timeout for Flash erase operations (in ms)
2476
2477- CONFIG_SYS_FLASH_WRITE_TOUT:
2478		Timeout for Flash write operations (in ms)
2479
2480- CONFIG_SYS_FLASH_LOCK_TOUT
2481		Timeout for Flash set sector lock bit operation (in ms)
2482
2483- CONFIG_SYS_FLASH_UNLOCK_TOUT
2484		Timeout for Flash clear lock bits operation (in ms)
2485
2486- CONFIG_SYS_FLASH_PROTECTION
2487		If defined, hardware flash sectors protection is used
2488		instead of U-Boot software protection.
2489
2490- CONFIG_SYS_DIRECT_FLASH_TFTP:
2491
2492		Enable TFTP transfers directly to flash memory;
2493		without this option such a download has to be
2494		performed in two steps: (1) download to RAM, and (2)
2495		copy from RAM to flash.
2496
2497		The two-step approach is usually more reliable, since
2498		you can check if the download worked before you erase
2499		the flash, but in some situations (when system RAM is
2500		too limited to allow for a temporary copy of the
2501		downloaded image) this option may be very useful.
2502
2503- CONFIG_SYS_FLASH_CFI:
2504		Define if the flash driver uses extra elements in the
2505		common flash structure for storing flash geometry.
2506
2507- CONFIG_FLASH_CFI_DRIVER
2508		This option also enables the building of the cfi_flash driver
2509		in the drivers directory
2510
2511- CONFIG_FLASH_CFI_MTD
2512		This option enables the building of the cfi_mtd driver
2513		in the drivers directory. The driver exports CFI flash
2514		to the MTD layer.
2515
2516- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2517		Use buffered writes to flash.
2518
2519- CONFIG_FLASH_SPANSION_S29WS_N
2520		s29ws-n MirrorBit flash has non-standard addresses for buffered
2521		write commands.
2522
2523- CONFIG_SYS_FLASH_QUIET_TEST
2524		If this option is defined, the common CFI flash doesn't
2525		print it's warning upon not recognized FLASH banks. This
2526		is useful, if some of the configured banks are only
2527		optionally available.
2528
2529- CONFIG_FLASH_SHOW_PROGRESS
2530		If defined (must be an integer), print out countdown
2531		digits and dots.  Recommended value: 45 (9..1) for 80
2532		column displays, 15 (3..1) for 40 column displays.
2533
2534- CONFIG_FLASH_VERIFY
2535		If defined, the content of the flash (destination) is compared
2536		against the source after the write operation. An error message
2537		will be printed when the contents are not identical.
2538		Please note that this option is useless in nearly all cases,
2539		since such flash programming errors usually are detected earlier
2540		while unprotecting/erasing/programming. Please only enable
2541		this option if you really know what you are doing.
2542
2543- CONFIG_SYS_RX_ETH_BUFFER:
2544		Defines the number of Ethernet receive buffers. On some
2545		Ethernet controllers it is recommended to set this value
2546		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2547		buffers can be full shortly after enabling the interface
2548		on high Ethernet traffic.
2549		Defaults to 4 if not defined.
2550
2551- CONFIG_ENV_MAX_ENTRIES
2552
2553	Maximum number of entries in the hash table that is used
2554	internally to store the environment settings. The default
2555	setting is supposed to be generous and should work in most
2556	cases. This setting can be used to tune behaviour; see
2557	lib/hashtable.c for details.
2558
2559- CONFIG_ENV_FLAGS_LIST_DEFAULT
2560- CONFIG_ENV_FLAGS_LIST_STATIC
2561	Enable validation of the values given to environment variables when
2562	calling env set.  Variables can be restricted to only decimal,
2563	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2564	the variables can also be restricted to IP address or MAC address.
2565
2566	The format of the list is:
2567		type_attribute = [s|d|x|b|i|m]
2568		access_attribute = [a|r|o|c]
2569		attributes = type_attribute[access_attribute]
2570		entry = variable_name[:attributes]
2571		list = entry[,list]
2572
2573	The type attributes are:
2574		s - String (default)
2575		d - Decimal
2576		x - Hexadecimal
2577		b - Boolean ([1yYtT|0nNfF])
2578		i - IP address
2579		m - MAC address
2580
2581	The access attributes are:
2582		a - Any (default)
2583		r - Read-only
2584		o - Write-once
2585		c - Change-default
2586
2587	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2588		Define this to a list (string) to define the ".flags"
2589		environment variable in the default or embedded environment.
2590
2591	- CONFIG_ENV_FLAGS_LIST_STATIC
2592		Define this to a list (string) to define validation that
2593		should be done if an entry is not found in the ".flags"
2594		environment variable.  To override a setting in the static
2595		list, simply add an entry for the same variable name to the
2596		".flags" variable.
2597
2598	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2599	regular expression. This allows multiple variables to define the same
2600	flags without explicitly listing them for each variable.
2601
2602The following definitions that deal with the placement and management
2603of environment data (variable area); in general, we support the
2604following configurations:
2605
2606- CONFIG_BUILD_ENVCRC:
2607
2608	Builds up envcrc with the target environment so that external utils
2609	may easily extract it and embed it in final U-Boot images.
2610
2611BE CAREFUL! The first access to the environment happens quite early
2612in U-Boot initialization (when we try to get the setting of for the
2613console baudrate). You *MUST* have mapped your NVRAM area then, or
2614U-Boot will hang.
2615
2616Please note that even with NVRAM we still use a copy of the
2617environment in RAM: we could work on NVRAM directly, but we want to
2618keep settings there always unmodified except somebody uses "saveenv"
2619to save the current settings.
2620
2621BE CAREFUL! For some special cases, the local device can not use
2622"saveenv" command. For example, the local device will get the
2623environment stored in a remote NOR flash by SRIO or PCIE link,
2624but it can not erase, write this NOR flash by SRIO or PCIE interface.
2625
2626- CONFIG_NAND_ENV_DST
2627
2628	Defines address in RAM to which the nand_spl code should copy the
2629	environment. If redundant environment is used, it will be copied to
2630	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2631
2632Please note that the environment is read-only until the monitor
2633has been relocated to RAM and a RAM copy of the environment has been
2634created; also, when using EEPROM you will have to use env_get_f()
2635until then to read environment variables.
2636
2637The environment is protected by a CRC32 checksum. Before the monitor
2638is relocated into RAM, as a result of a bad CRC you will be working
2639with the compiled-in default environment - *silently*!!! [This is
2640necessary, because the first environment variable we need is the
2641"baudrate" setting for the console - if we have a bad CRC, we don't
2642have any device yet where we could complain.]
2643
2644Note: once the monitor has been relocated, then it will complain if
2645the default environment is used; a new CRC is computed as soon as you
2646use the "saveenv" command to store a valid environment.
2647
2648- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2649		Echo the inverted Ethernet link state to the fault LED.
2650
2651		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2652		      also needs to be defined.
2653
2654- CONFIG_SYS_FAULT_MII_ADDR:
2655		MII address of the PHY to check for the Ethernet link state.
2656
2657- CONFIG_NS16550_MIN_FUNCTIONS:
2658		Define this if you desire to only have use of the NS16550_init
2659		and NS16550_putc functions for the serial driver located at
2660		drivers/serial/ns16550.c.  This option is useful for saving
2661		space for already greatly restricted images, including but not
2662		limited to NAND_SPL configurations.
2663
2664- CONFIG_DISPLAY_BOARDINFO
2665		Display information about the board that U-Boot is running on
2666		when U-Boot starts up. The board function checkboard() is called
2667		to do this.
2668
2669- CONFIG_DISPLAY_BOARDINFO_LATE
2670		Similar to the previous option, but display this information
2671		later, once stdio is running and output goes to the LCD, if
2672		present.
2673
2674- CONFIG_BOARD_SIZE_LIMIT:
2675		Maximum size of the U-Boot image. When defined, the
2676		build system checks that the actual size does not
2677		exceed it.
2678
2679Low Level (hardware related) configuration options:
2680---------------------------------------------------
2681
2682- CONFIG_SYS_CACHELINE_SIZE:
2683		Cache Line Size of the CPU.
2684
2685- CONFIG_SYS_CCSRBAR_DEFAULT:
2686		Default (power-on reset) physical address of CCSR on Freescale
2687		PowerPC SOCs.
2688
2689- CONFIG_SYS_CCSRBAR:
2690		Virtual address of CCSR.  On a 32-bit build, this is typically
2691		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2692
2693- CONFIG_SYS_CCSRBAR_PHYS:
2694		Physical address of CCSR.  CCSR can be relocated to a new
2695		physical address, if desired.  In this case, this macro should
2696		be set to that address.	 Otherwise, it should be set to the
2697		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2698		is typically relocated on 36-bit builds.  It is recommended
2699		that this macro be defined via the _HIGH and _LOW macros:
2700
2701		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2702			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2703
2704- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2705		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
2706		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
2707		used in assembly code, so it must not contain typecasts or
2708		integer size suffixes (e.g. "ULL").
2709
2710- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2711		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2712		used in assembly code, so it must not contain typecasts or
2713		integer size suffixes (e.g. "ULL").
2714
2715- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2716		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2717		forced to a value that ensures that CCSR is not relocated.
2718
2719- CONFIG_IDE_AHB:
2720		Most IDE controllers were designed to be connected with PCI
2721		interface. Only few of them were designed for AHB interface.
2722		When software is doing ATA command and data transfer to
2723		IDE devices through IDE-AHB controller, some additional
2724		registers accessing to these kind of IDE-AHB controller
2725		is required.
2726
2727- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
2728		DO NOT CHANGE unless you know exactly what you're
2729		doing! (11-4) [MPC8xx systems only]
2730
2731- CONFIG_SYS_INIT_RAM_ADDR:
2732
2733		Start address of memory area that can be used for
2734		initial data and stack; please note that this must be
2735		writable memory that is working WITHOUT special
2736		initialization, i. e. you CANNOT use normal RAM which
2737		will become available only after programming the
2738		memory controller and running certain initialization
2739		sequences.
2740
2741		U-Boot uses the following memory types:
2742		- MPC8xx: IMMR (internal memory of the CPU)
2743
2744- CONFIG_SYS_GBL_DATA_OFFSET:
2745
2746		Offset of the initial data structure in the memory
2747		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2748		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2749		data is located at the end of the available space
2750		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2751		GENERATED_GBL_DATA_SIZE), and the initial stack is just
2752		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2753		CONFIG_SYS_GBL_DATA_OFFSET) downward.
2754
2755	Note:
2756		On the MPC824X (or other systems that use the data
2757		cache for initial memory) the address chosen for
2758		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2759		point to an otherwise UNUSED address space between
2760		the top of RAM and the start of the PCI space.
2761
2762- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
2763
2764- CONFIG_SYS_OR_TIMING_SDRAM:
2765		SDRAM timing
2766
2767- CONFIG_SYS_MAMR_PTA:
2768		periodic timer for refresh
2769
2770- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2771  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2772  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2773  CONFIG_SYS_BR1_PRELIM:
2774		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2775
2776- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2777  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2778  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2779		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2780
2781- CONFIG_PCI_INDIRECT_BRIDGE:
2782		Enable support for indirect PCI bridges.
2783
2784- CONFIG_SYS_SRIO:
2785		Chip has SRIO or not
2786
2787- CONFIG_SRIO1:
2788		Board has SRIO 1 port available
2789
2790- CONFIG_SRIO2:
2791		Board has SRIO 2 port available
2792
2793- CONFIG_SRIO_PCIE_BOOT_MASTER
2794		Board can support master function for Boot from SRIO and PCIE
2795
2796- CONFIG_SYS_SRIOn_MEM_VIRT:
2797		Virtual Address of SRIO port 'n' memory region
2798
2799- CONFIG_SYS_SRIOn_MEM_PHYxS:
2800		Physical Address of SRIO port 'n' memory region
2801
2802- CONFIG_SYS_SRIOn_MEM_SIZE:
2803		Size of SRIO port 'n' memory region
2804
2805- CONFIG_SYS_NAND_BUSWIDTH_16BIT
2806		Defined to tell the NAND controller that the NAND chip is using
2807		a 16 bit bus.
2808		Not all NAND drivers use this symbol.
2809		Example of drivers that use it:
2810		- drivers/mtd/nand/raw/ndfc.c
2811		- drivers/mtd/nand/raw/mxc_nand.c
2812
2813- CONFIG_SYS_NDFC_EBC0_CFG
2814		Sets the EBC0_CFG register for the NDFC. If not defined
2815		a default value will be used.
2816
2817- CONFIG_SPD_EEPROM
2818		Get DDR timing information from an I2C EEPROM. Common
2819		with pluggable memory modules such as SODIMMs
2820
2821  SPD_EEPROM_ADDRESS
2822		I2C address of the SPD EEPROM
2823
2824- CONFIG_SYS_SPD_BUS_NUM
2825		If SPD EEPROM is on an I2C bus other than the first
2826		one, specify here. Note that the value must resolve
2827		to something your driver can deal with.
2828
2829- CONFIG_SYS_DDR_RAW_TIMING
2830		Get DDR timing information from other than SPD. Common with
2831		soldered DDR chips onboard without SPD. DDR raw timing
2832		parameters are extracted from datasheet and hard-coded into
2833		header files or board specific files.
2834
2835- CONFIG_FSL_DDR_INTERACTIVE
2836		Enable interactive DDR debugging. See doc/README.fsl-ddr.
2837
2838- CONFIG_FSL_DDR_SYNC_REFRESH
2839		Enable sync of refresh for multiple controllers.
2840
2841- CONFIG_FSL_DDR_BIST
2842		Enable built-in memory test for Freescale DDR controllers.
2843
2844- CONFIG_SYS_83XX_DDR_USES_CS0
2845		Only for 83xx systems. If specified, then DDR should
2846		be configured using CS0 and CS1 instead of CS2 and CS3.
2847
2848- CONFIG_RMII
2849		Enable RMII mode for all FECs.
2850		Note that this is a global option, we can't
2851		have one FEC in standard MII mode and another in RMII mode.
2852
2853- CONFIG_CRC32_VERIFY
2854		Add a verify option to the crc32 command.
2855		The syntax is:
2856
2857		=> crc32 -v <address> <count> <crc32>
2858
2859		Where address/count indicate a memory area
2860		and crc32 is the correct crc32 which the
2861		area should have.
2862
2863- CONFIG_LOOPW
2864		Add the "loopw" memory command. This only takes effect if
2865		the memory commands are activated globally (CONFIG_CMD_MEMORY).
2866
2867- CONFIG_CMD_MX_CYCLIC
2868		Add the "mdc" and "mwc" memory commands. These are cyclic
2869		"md/mw" commands.
2870		Examples:
2871
2872		=> mdc.b 10 4 500
2873		This command will print 4 bytes (10,11,12,13) each 500 ms.
2874
2875		=> mwc.l 100 12345678 10
2876		This command will write 12345678 to address 100 all 10 ms.
2877
2878		This only takes effect if the memory commands are activated
2879		globally (CONFIG_CMD_MEMORY).
2880
2881- CONFIG_SKIP_LOWLEVEL_INIT
2882		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2883		low level initializations (like setting up the memory
2884		controller) are omitted and/or U-Boot does not
2885		relocate itself into RAM.
2886
2887		Normally this variable MUST NOT be defined. The only
2888		exception is when U-Boot is loaded (to RAM) by some
2889		other boot loader or by a debugger which performs
2890		these initializations itself.
2891
2892- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
2893		[ARM926EJ-S only] This allows just the call to lowlevel_init()
2894		to be skipped. The normal CP15 init (such as enabling the
2895		instruction cache) is still performed.
2896
2897- CONFIG_SPL_BUILD
2898		Set when the currently-running compilation is for an artifact
2899		that will end up in the SPL (as opposed to the TPL or U-Boot
2900		proper). Code that needs stage-specific behavior should check
2901		this.
2902
2903- CONFIG_TPL_BUILD
2904		Set when the currently-running compilation is for an artifact
2905		that will end up in the TPL (as opposed to the SPL or U-Boot
2906		proper). Code that needs stage-specific behavior should check
2907		this.
2908
2909- CONFIG_SYS_MPC85XX_NO_RESETVEC
2910		Only for 85xx systems. If this variable is specified, the section
2911		.resetvec is not kept and the section .bootpg is placed in the
2912		previous 4k of the .text section.
2913
2914- CONFIG_ARCH_MAP_SYSMEM
2915		Generally U-Boot (and in particular the md command) uses
2916		effective address. It is therefore not necessary to regard
2917		U-Boot address as virtual addresses that need to be translated
2918		to physical addresses. However, sandbox requires this, since
2919		it maintains its own little RAM buffer which contains all
2920		addressable memory. This option causes some memory accesses
2921		to be mapped through map_sysmem() / unmap_sysmem().
2922
2923- CONFIG_X86_RESET_VECTOR
2924		If defined, the x86 reset vector code is included. This is not
2925		needed when U-Boot is running from Coreboot.
2926
2927- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2928		Option to disable subpage write in NAND driver
2929		driver that uses this:
2930		drivers/mtd/nand/raw/davinci_nand.c
2931
2932Freescale QE/FMAN Firmware Support:
2933-----------------------------------
2934
2935The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2936loading of "firmware", which is encoded in the QE firmware binary format.
2937This firmware often needs to be loaded during U-Boot booting, so macros
2938are used to identify the storage device (NOR flash, SPI, etc) and the address
2939within that device.
2940
2941- CONFIG_SYS_FMAN_FW_ADDR
2942	The address in the storage device where the FMAN microcode is located.  The
2943	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2944	is also specified.
2945
2946- CONFIG_SYS_QE_FW_ADDR
2947	The address in the storage device where the QE microcode is located.  The
2948	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2949	is also specified.
2950
2951- CONFIG_SYS_QE_FMAN_FW_LENGTH
2952	The maximum possible size of the firmware.  The firmware binary format
2953	has a field that specifies the actual size of the firmware, but it
2954	might not be possible to read any part of the firmware unless some
2955	local storage is allocated to hold the entire firmware first.
2956
2957- CONFIG_SYS_QE_FMAN_FW_IN_NOR
2958	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2959	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
2960	virtual address in NOR flash.
2961
2962- CONFIG_SYS_QE_FMAN_FW_IN_NAND
2963	Specifies that QE/FMAN firmware is located in NAND flash.
2964	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2965
2966- CONFIG_SYS_QE_FMAN_FW_IN_MMC
2967	Specifies that QE/FMAN firmware is located on the primary SD/MMC
2968	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2969
2970- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2971	Specifies that QE/FMAN firmware is located in the remote (master)
2972	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2973	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2974	window->master inbound window->master LAW->the ucode address in
2975	master's memory space.
2976
2977Freescale Layerscape Management Complex Firmware Support:
2978---------------------------------------------------------
2979The Freescale Layerscape Management Complex (MC) supports the loading of
2980"firmware".
2981This firmware often needs to be loaded during U-Boot booting, so macros
2982are used to identify the storage device (NOR flash, SPI, etc) and the address
2983within that device.
2984
2985- CONFIG_FSL_MC_ENET
2986	Enable the MC driver for Layerscape SoCs.
2987
2988Freescale Layerscape Debug Server Support:
2989-------------------------------------------
2990The Freescale Layerscape Debug Server Support supports the loading of
2991"Debug Server firmware" and triggering SP boot-rom.
2992This firmware often needs to be loaded during U-Boot booting.
2993
2994- CONFIG_SYS_MC_RSV_MEM_ALIGN
2995	Define alignment of reserved memory MC requires
2996
2997Reproducible builds
2998-------------------
2999
3000In order to achieve reproducible builds, timestamps used in the U-Boot build
3001process have to be set to a fixed value.
3002
3003This is done using the SOURCE_DATE_EPOCH environment variable.
3004SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3005option for U-Boot or an environment variable in U-Boot.
3006
3007SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3008
3009Building the Software:
3010======================
3011
3012Building U-Boot has been tested in several native build environments
3013and in many different cross environments. Of course we cannot support
3014all possibly existing versions of cross development tools in all
3015(potentially obsolete) versions. In case of tool chain problems we
3016recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
3017which is extensively used to build and test U-Boot.
3018
3019If you are not using a native environment, it is assumed that you
3020have GNU cross compiling tools available in your path. In this case,
3021you must set the environment variable CROSS_COMPILE in your shell.
3022Note that no changes to the Makefile or any other source files are
3023necessary. For example using the ELDK on a 4xx CPU, please enter:
3024
3025	$ CROSS_COMPILE=ppc_4xx-
3026	$ export CROSS_COMPILE
3027
3028U-Boot is intended to be simple to build. After installing the
3029sources you must configure U-Boot for one specific board type. This
3030is done by typing:
3031
3032	make NAME_defconfig
3033
3034where "NAME_defconfig" is the name of one of the existing configu-
3035rations; see configs/*_defconfig for supported names.
3036
3037Note: for some boards special configuration names may exist; check if
3038      additional information is available from the board vendor; for
3039      instance, the TQM823L systems are available without (standard)
3040      or with LCD support. You can select such additional "features"
3041      when choosing the configuration, i. e.
3042
3043      make TQM823L_defconfig
3044	- will configure for a plain TQM823L, i. e. no LCD support
3045
3046      make TQM823L_LCD_defconfig
3047	- will configure for a TQM823L with U-Boot console on LCD
3048
3049      etc.
3050
3051
3052Finally, type "make all", and you should get some working U-Boot
3053images ready for download to / installation on your system:
3054
3055- "u-boot.bin" is a raw binary image
3056- "u-boot" is an image in ELF binary format
3057- "u-boot.srec" is in Motorola S-Record format
3058
3059By default the build is performed locally and the objects are saved
3060in the source directory. One of the two methods can be used to change
3061this behavior and build U-Boot to some external directory:
3062
30631. Add O= to the make command line invocations:
3064
3065	make O=/tmp/build distclean
3066	make O=/tmp/build NAME_defconfig
3067	make O=/tmp/build all
3068
30692. Set environment variable KBUILD_OUTPUT to point to the desired location:
3070
3071	export KBUILD_OUTPUT=/tmp/build
3072	make distclean
3073	make NAME_defconfig
3074	make all
3075
3076Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3077variable.
3078
3079User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3080setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3081For example to treat all compiler warnings as errors:
3082
3083	make KCFLAGS=-Werror
3084
3085Please be aware that the Makefiles assume you are using GNU make, so
3086for instance on NetBSD you might need to use "gmake" instead of
3087native "make".
3088
3089
3090If the system board that you have is not listed, then you will need
3091to port U-Boot to your hardware platform. To do this, follow these
3092steps:
3093
30941.  Create a new directory to hold your board specific code. Add any
3095    files you need. In your board directory, you will need at least
3096    the "Makefile" and a "<board>.c".
30972.  Create a new configuration file "include/configs/<board>.h" for
3098    your board.
30993.  If you're porting U-Boot to a new CPU, then also create a new
3100    directory to hold your CPU specific code. Add any files you need.
31014.  Run "make <board>_defconfig" with your new name.
31025.  Type "make", and you should get a working "u-boot.srec" file
3103    to be installed on your target system.
31046.  Debug and solve any problems that might arise.
3105    [Of course, this last step is much harder than it sounds.]
3106
3107
3108Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3109==============================================================
3110
3111If you have modified U-Boot sources (for instance added a new board
3112or support for new devices, a new CPU, etc.) you are expected to
3113provide feedback to the other developers. The feedback normally takes
3114the form of a "patch", i.e. a context diff against a certain (latest
3115official or latest in the git repository) version of U-Boot sources.
3116
3117But before you submit such a patch, please verify that your modifi-
3118cation did not break existing code. At least make sure that *ALL* of
3119the supported boards compile WITHOUT ANY compiler warnings. To do so,
3120just run the buildman script (tools/buildman/buildman), which will
3121configure and build U-Boot for ALL supported system. Be warned, this
3122will take a while. Please see the buildman README, or run 'buildman -H'
3123for documentation.
3124
3125
3126See also "U-Boot Porting Guide" below.
3127
3128
3129Monitor Commands - Overview:
3130============================
3131
3132go	- start application at address 'addr'
3133run	- run commands in an environment variable
3134bootm	- boot application image from memory
3135bootp	- boot image via network using BootP/TFTP protocol
3136bootz   - boot zImage from memory
3137tftpboot- boot image via network using TFTP protocol
3138	       and env variables "ipaddr" and "serverip"
3139	       (and eventually "gatewayip")
3140tftpput - upload a file via network using TFTP protocol
3141rarpboot- boot image via network using RARP/TFTP protocol
3142diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3143loads	- load S-Record file over serial line
3144loadb	- load binary file over serial line (kermit mode)
3145md	- memory display
3146mm	- memory modify (auto-incrementing)
3147nm	- memory modify (constant address)
3148mw	- memory write (fill)
3149ms	- memory search
3150cp	- memory copy
3151cmp	- memory compare
3152crc32	- checksum calculation
3153i2c	- I2C sub-system
3154sspi	- SPI utility commands
3155base	- print or set address offset
3156printenv- print environment variables
3157pwm	- control pwm channels
3158setenv	- set environment variables
3159saveenv - save environment variables to persistent storage
3160protect - enable or disable FLASH write protection
3161erase	- erase FLASH memory
3162flinfo	- print FLASH memory information
3163nand	- NAND memory operations (see doc/README.nand)
3164bdinfo	- print Board Info structure
3165iminfo	- print header information for application image
3166coninfo - print console devices and informations
3167ide	- IDE sub-system
3168loop	- infinite loop on address range
3169loopw	- infinite write loop on address range
3170mtest	- simple RAM test
3171icache	- enable or disable instruction cache
3172dcache	- enable or disable data cache
3173reset	- Perform RESET of the CPU
3174echo	- echo args to console
3175version - print monitor version
3176help	- print online help
3177?	- alias for 'help'
3178
3179
3180Monitor Commands - Detailed Description:
3181========================================
3182
3183TODO.
3184
3185For now: just type "help <command>".
3186
3187
3188Environment Variables:
3189======================
3190
3191U-Boot supports user configuration using Environment Variables which
3192can be made persistent by saving to Flash memory.
3193
3194Environment Variables are set using "setenv", printed using
3195"printenv", and saved to Flash using "saveenv". Using "setenv"
3196without a value can be used to delete a variable from the
3197environment. As long as you don't save the environment you are
3198working with an in-memory copy. In case the Flash area containing the
3199environment is erased by accident, a default environment is provided.
3200
3201Some configuration options can be set using Environment Variables.
3202
3203List of environment variables (most likely not complete):
3204
3205  baudrate	- see CONFIG_BAUDRATE
3206
3207  bootdelay	- see CONFIG_BOOTDELAY
3208
3209  bootcmd	- see CONFIG_BOOTCOMMAND
3210
3211  bootargs	- Boot arguments when booting an RTOS image
3212
3213  bootfile	- Name of the image to load with TFTP
3214
3215  bootm_low	- Memory range available for image processing in the bootm
3216		  command can be restricted. This variable is given as
3217		  a hexadecimal number and defines lowest address allowed
3218		  for use by the bootm command. See also "bootm_size"
3219		  environment variable. Address defined by "bootm_low" is
3220		  also the base of the initial memory mapping for the Linux
3221		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3222		  bootm_mapsize.
3223
3224  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3225		  This variable is given as a hexadecimal number and it
3226		  defines the size of the memory region starting at base
3227		  address bootm_low that is accessible by the Linux kernel
3228		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3229		  as the default value if it is defined, and bootm_size is
3230		  used otherwise.
3231
3232  bootm_size	- Memory range available for image processing in the bootm
3233		  command can be restricted. This variable is given as
3234		  a hexadecimal number and defines the size of the region
3235		  allowed for use by the bootm command. See also "bootm_low"
3236		  environment variable.
3237
3238  bootstopkeysha256, bootdelaykey, bootstopkey	- See README.autoboot
3239
3240  updatefile	- Location of the software update file on a TFTP server, used
3241		  by the automatic software update feature. Please refer to
3242		  documentation in doc/README.update for more details.
3243
3244  autoload	- if set to "no" (any string beginning with 'n'),
3245		  "bootp" will just load perform a lookup of the
3246		  configuration from the BOOTP server, but not try to
3247		  load any image using TFTP
3248
3249  autostart	- if set to "yes", an image loaded using the "bootp",
3250		  "rarpboot", "tftpboot" or "diskboot" commands will
3251		  be automatically started (by internally calling
3252		  "bootm")
3253
3254		  If set to "no", a standalone image passed to the
3255		  "bootm" command will be copied to the load address
3256		  (and eventually uncompressed), but NOT be started.
3257		  This can be used to load and uncompress arbitrary
3258		  data.
3259
3260  fdt_high	- if set this restricts the maximum address that the
3261		  flattened device tree will be copied into upon boot.
3262		  For example, if you have a system with 1 GB memory
3263		  at physical address 0x10000000, while Linux kernel
3264		  only recognizes the first 704 MB as low memory, you
3265		  may need to set fdt_high as 0x3C000000 to have the
3266		  device tree blob be copied to the maximum address
3267		  of the 704 MB low memory, so that Linux kernel can
3268		  access it during the boot procedure.
3269
3270		  If this is set to the special value 0xFFFFFFFF then
3271		  the fdt will not be copied at all on boot.  For this
3272		  to work it must reside in writable memory, have
3273		  sufficient padding on the end of it for u-boot to
3274		  add the information it needs into it, and the memory
3275		  must be accessible by the kernel.
3276
3277  fdtcontroladdr- if set this is the address of the control flattened
3278		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3279		  defined.
3280
3281  i2cfast	- (PPC405GP|PPC405EP only)
3282		  if set to 'y' configures Linux I2C driver for fast
3283		  mode (400kHZ). This environment variable is used in
3284		  initialization code. So, for changes to be effective
3285		  it must be saved and board must be reset.
3286
3287  initrd_high	- restrict positioning of initrd images:
3288		  If this variable is not set, initrd images will be
3289		  copied to the highest possible address in RAM; this
3290		  is usually what you want since it allows for
3291		  maximum initrd size. If for some reason you want to
3292		  make sure that the initrd image is loaded below the
3293		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3294		  variable to a value of "no" or "off" or "0".
3295		  Alternatively, you can set it to a maximum upper
3296		  address to use (U-Boot will still check that it
3297		  does not overwrite the U-Boot stack and data).
3298
3299		  For instance, when you have a system with 16 MB
3300		  RAM, and want to reserve 4 MB from use by Linux,
3301		  you can do this by adding "mem=12M" to the value of
3302		  the "bootargs" variable. However, now you must make
3303		  sure that the initrd image is placed in the first
3304		  12 MB as well - this can be done with
3305
3306		  setenv initrd_high 00c00000
3307
3308		  If you set initrd_high to 0xFFFFFFFF, this is an
3309		  indication to U-Boot that all addresses are legal
3310		  for the Linux kernel, including addresses in flash
3311		  memory. In this case U-Boot will NOT COPY the
3312		  ramdisk at all. This may be useful to reduce the
3313		  boot time on your system, but requires that this
3314		  feature is supported by your Linux kernel.
3315
3316  ipaddr	- IP address; needed for tftpboot command
3317
3318  loadaddr	- Default load address for commands like "bootp",
3319		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3320
3321  loads_echo	- see CONFIG_LOADS_ECHO
3322
3323  serverip	- TFTP server IP address; needed for tftpboot command
3324
3325  bootretry	- see CONFIG_BOOT_RETRY_TIME
3326
3327  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3328
3329  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3330
3331  ethprime	- controls which interface is used first.
3332
3333  ethact	- controls which interface is currently active.
3334		  For example you can do the following
3335
3336		  => setenv ethact FEC
3337		  => ping 192.168.0.1 # traffic sent on FEC
3338		  => setenv ethact SCC
3339		  => ping 10.0.0.1 # traffic sent on SCC
3340
3341  ethrotate	- When set to "no" U-Boot does not go through all
3342		  available network interfaces.
3343		  It just stays at the currently selected interface.
3344
3345  netretry	- When set to "no" each network operation will
3346		  either succeed or fail without retrying.
3347		  When set to "once" the network operation will
3348		  fail when all the available network interfaces
3349		  are tried once without success.
3350		  Useful on scripts which control the retry operation
3351		  themselves.
3352
3353  npe_ucode	- set load address for the NPE microcode
3354
3355  silent_linux  - If set then Linux will be told to boot silently, by
3356		  changing the console to be empty. If "yes" it will be
3357		  made silent. If "no" it will not be made silent. If
3358		  unset, then it will be made silent if the U-Boot console
3359		  is silent.
3360
3361  tftpsrcp	- If this is set, the value is used for TFTP's
3362		  UDP source port.
3363
3364  tftpdstp	- If this is set, the value is used for TFTP's UDP
3365		  destination port instead of the Well Know Port 69.
3366
3367  tftpblocksize - Block size to use for TFTP transfers; if not set,
3368		  we use the TFTP server's default block size
3369
3370  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3371		  seconds, minimum value is 1000 = 1 second). Defines
3372		  when a packet is considered to be lost so it has to
3373		  be retransmitted. The default is 5000 = 5 seconds.
3374		  Lowering this value may make downloads succeed
3375		  faster in networks with high packet loss rates or
3376		  with unreliable TFTP servers.
3377
3378  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3379		  unit, minimum value = 0). Defines how many timeouts
3380		  can happen during a single file transfer before that
3381		  transfer is aborted. The default is 10, and 0 means
3382		  'no timeouts allowed'. Increasing this value may help
3383		  downloads succeed with high packet loss rates, or with
3384		  unreliable TFTP servers or client hardware.
3385
3386  tftpwindowsize	- if this is set, the value is used for TFTP's
3387		  window size as described by RFC 7440.
3388		  This means the count of blocks we can receive before
3389		  sending ack to server.
3390
3391  vlan		- When set to a value < 4095 the traffic over
3392		  Ethernet is encapsulated/received over 802.1q
3393		  VLAN tagged frames.
3394
3395  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3396		  Unsigned value, in milliseconds. If not set, the period will
3397		  be either the default (28000), or a value based on
3398		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3399		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3400
3401  memmatches	- Number of matches found by the last 'ms' command, in hex
3402
3403  memaddr	- Address of the last match found by the 'ms' command, in hex,
3404		  or 0 if none
3405
3406  mempos	- Index position of the last match found by the 'ms' command,
3407		  in units of the size (.b, .w, .l) of the search
3408
3409  zbootbase	- (x86 only) Base address of the bzImage 'setup' block
3410
3411  zbootaddr	- (x86 only) Address of the loaded bzImage, typically
3412		  BZIMAGE_LOAD_ADDR which is 0x100000
3413
3414The following image location variables contain the location of images
3415used in booting. The "Image" column gives the role of the image and is
3416not an environment variable name. The other columns are environment
3417variable names. "File Name" gives the name of the file on a TFTP
3418server, "RAM Address" gives the location in RAM the image will be
3419loaded to, and "Flash Location" gives the image's address in NOR
3420flash or offset in NAND flash.
3421
3422*Note* - these variables don't have to be defined for all boards, some
3423boards currently use other variables for these purposes, and some
3424boards use these variables for other purposes.
3425
3426Image		    File Name	     RAM Address       Flash Location
3427-----		    ---------	     -----------       --------------
3428u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3429Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3430device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3431ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3432
3433The following environment variables may be used and automatically
3434updated by the network boot commands ("bootp" and "rarpboot"),
3435depending the information provided by your boot server:
3436
3437  bootfile	- see above
3438  dnsip		- IP address of your Domain Name Server
3439  dnsip2	- IP address of your secondary Domain Name Server
3440  gatewayip	- IP address of the Gateway (Router) to use
3441  hostname	- Target hostname
3442  ipaddr	- see above
3443  netmask	- Subnet Mask
3444  rootpath	- Pathname of the root filesystem on the NFS server
3445  serverip	- see above
3446
3447
3448There are two special Environment Variables:
3449
3450  serial#	- contains hardware identification information such
3451		  as type string and/or serial number
3452  ethaddr	- Ethernet address
3453
3454These variables can be set only once (usually during manufacturing of
3455the board). U-Boot refuses to delete or overwrite these variables
3456once they have been set once.
3457
3458
3459Further special Environment Variables:
3460
3461  ver		- Contains the U-Boot version string as printed
3462		  with the "version" command. This variable is
3463		  readonly (see CONFIG_VERSION_VARIABLE).
3464
3465
3466Please note that changes to some configuration parameters may take
3467only effect after the next boot (yes, that's just like Windoze :-).
3468
3469
3470Callback functions for environment variables:
3471---------------------------------------------
3472
3473For some environment variables, the behavior of u-boot needs to change
3474when their values are changed.  This functionality allows functions to
3475be associated with arbitrary variables.  On creation, overwrite, or
3476deletion, the callback will provide the opportunity for some side
3477effect to happen or for the change to be rejected.
3478
3479The callbacks are named and associated with a function using the
3480U_BOOT_ENV_CALLBACK macro in your board or driver code.
3481
3482These callbacks are associated with variables in one of two ways.  The
3483static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3484in the board configuration to a string that defines a list of
3485associations.  The list must be in the following format:
3486
3487	entry = variable_name[:callback_name]
3488	list = entry[,list]
3489
3490If the callback name is not specified, then the callback is deleted.
3491Spaces are also allowed anywhere in the list.
3492
3493Callbacks can also be associated by defining the ".callbacks" variable
3494with the same list format above.  Any association in ".callbacks" will
3495override any association in the static list. You can define
3496CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3497".callbacks" environment variable in the default or embedded environment.
3498
3499If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3500regular expression. This allows multiple variables to be connected to
3501the same callback without explicitly listing them all out.
3502
3503The signature of the callback functions is:
3504
3505    int callback(const char *name, const char *value, enum env_op op, int flags)
3506
3507* name - changed environment variable
3508* value - new value of the environment variable
3509* op - operation (create, overwrite, or delete)
3510* flags - attributes of the environment variable change, see flags H_* in
3511  include/search.h
3512
3513The return value is 0 if the variable change is accepted and 1 otherwise.
3514
3515Command Line Parsing:
3516=====================
3517
3518There are two different command line parsers available with U-Boot:
3519the old "simple" one, and the much more powerful "hush" shell:
3520
3521Old, simple command line parser:
3522--------------------------------
3523
3524- supports environment variables (through setenv / saveenv commands)
3525- several commands on one line, separated by ';'
3526- variable substitution using "... ${name} ..." syntax
3527- special characters ('$', ';') can be escaped by prefixing with '\',
3528  for example:
3529	setenv bootcmd bootm \${address}
3530- You can also escape text by enclosing in single apostrophes, for example:
3531	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3532
3533Hush shell:
3534-----------
3535
3536- similar to Bourne shell, with control structures like
3537  if...then...else...fi, for...do...done; while...do...done,
3538  until...do...done, ...
3539- supports environment ("global") variables (through setenv / saveenv
3540  commands) and local shell variables (through standard shell syntax
3541  "name=value"); only environment variables can be used with "run"
3542  command
3543
3544General rules:
3545--------------
3546
3547(1) If a command line (or an environment variable executed by a "run"
3548    command) contains several commands separated by semicolon, and
3549    one of these commands fails, then the remaining commands will be
3550    executed anyway.
3551
3552(2) If you execute several variables with one call to run (i. e.
3553    calling run with a list of variables as arguments), any failing
3554    command will cause "run" to terminate, i. e. the remaining
3555    variables are not executed.
3556
3557Note for Redundant Ethernet Interfaces:
3558=======================================
3559
3560Some boards come with redundant Ethernet interfaces; U-Boot supports
3561such configurations and is capable of automatic selection of a
3562"working" interface when needed. MAC assignment works as follows:
3563
3564Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3565MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3566"eth1addr" (=>eth1), "eth2addr", ...
3567
3568If the network interface stores some valid MAC address (for instance
3569in SROM), this is used as default address if there is NO correspon-
3570ding setting in the environment; if the corresponding environment
3571variable is set, this overrides the settings in the card; that means:
3572
3573o If the SROM has a valid MAC address, and there is no address in the
3574  environment, the SROM's address is used.
3575
3576o If there is no valid address in the SROM, and a definition in the
3577  environment exists, then the value from the environment variable is
3578  used.
3579
3580o If both the SROM and the environment contain a MAC address, and
3581  both addresses are the same, this MAC address is used.
3582
3583o If both the SROM and the environment contain a MAC address, and the
3584  addresses differ, the value from the environment is used and a
3585  warning is printed.
3586
3587o If neither SROM nor the environment contain a MAC address, an error
3588  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3589  a random, locally-assigned MAC is used.
3590
3591If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3592will be programmed into hardware as part of the initialization process.	 This
3593may be skipped by setting the appropriate 'ethmacskip' environment variable.
3594The naming convention is as follows:
3595"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3596
3597Image Formats:
3598==============
3599
3600U-Boot is capable of booting (and performing other auxiliary operations on)
3601images in two formats:
3602
3603New uImage format (FIT)
3604-----------------------
3605
3606Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3607to Flattened Device Tree). It allows the use of images with multiple
3608components (several kernels, ramdisks, etc.), with contents protected by
3609SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3610
3611
3612Old uImage format
3613-----------------
3614
3615Old image format is based on binary files which can be basically anything,
3616preceded by a special header; see the definitions in include/image.h for
3617details; basically, the header defines the following image properties:
3618
3619* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3620  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3621  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3622  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3623  INTEGRITY).
3624* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3625  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3626  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3627* Compression Type (uncompressed, gzip, bzip2)
3628* Load Address
3629* Entry Point
3630* Image Name
3631* Image Timestamp
3632
3633The header is marked by a special Magic Number, and both the header
3634and the data portions of the image are secured against corruption by
3635CRC32 checksums.
3636
3637
3638Linux Support:
3639==============
3640
3641Although U-Boot should support any OS or standalone application
3642easily, the main focus has always been on Linux during the design of
3643U-Boot.
3644
3645U-Boot includes many features that so far have been part of some
3646special "boot loader" code within the Linux kernel. Also, any
3647"initrd" images to be used are no longer part of one big Linux image;
3648instead, kernel and "initrd" are separate images. This implementation
3649serves several purposes:
3650
3651- the same features can be used for other OS or standalone
3652  applications (for instance: using compressed images to reduce the
3653  Flash memory footprint)
3654
3655- it becomes much easier to port new Linux kernel versions because
3656  lots of low-level, hardware dependent stuff are done by U-Boot
3657
3658- the same Linux kernel image can now be used with different "initrd"
3659  images; of course this also means that different kernel images can
3660  be run with the same "initrd". This makes testing easier (you don't
3661  have to build a new "zImage.initrd" Linux image when you just
3662  change a file in your "initrd"). Also, a field-upgrade of the
3663  software is easier now.
3664
3665
3666Linux HOWTO:
3667============
3668
3669Porting Linux to U-Boot based systems:
3670---------------------------------------
3671
3672U-Boot cannot save you from doing all the necessary modifications to
3673configure the Linux device drivers for use with your target hardware
3674(no, we don't intend to provide a full virtual machine interface to
3675Linux :-).
3676
3677But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3678
3679Just make sure your machine specific header file (for instance
3680include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3681Information structure as we define in include/asm-<arch>/u-boot.h,
3682and make sure that your definition of IMAP_ADDR uses the same value
3683as your U-Boot configuration in CONFIG_SYS_IMMR.
3684
3685Note that U-Boot now has a driver model, a unified model for drivers.
3686If you are adding a new driver, plumb it into driver model. If there
3687is no uclass available, you are encouraged to create one. See
3688doc/driver-model.
3689
3690
3691Configuring the Linux kernel:
3692-----------------------------
3693
3694No specific requirements for U-Boot. Make sure you have some root
3695device (initial ramdisk, NFS) for your target system.
3696
3697
3698Building a Linux Image:
3699-----------------------
3700
3701With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3702not used. If you use recent kernel source, a new build target
3703"uImage" will exist which automatically builds an image usable by
3704U-Boot. Most older kernels also have support for a "pImage" target,
3705which was introduced for our predecessor project PPCBoot and uses a
3706100% compatible format.
3707
3708Example:
3709
3710	make TQM850L_defconfig
3711	make oldconfig
3712	make dep
3713	make uImage
3714
3715The "uImage" build target uses a special tool (in 'tools/mkimage') to
3716encapsulate a compressed Linux kernel image with header	 information,
3717CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3718
3719* build a standard "vmlinux" kernel image (in ELF binary format):
3720
3721* convert the kernel into a raw binary image:
3722
3723	${CROSS_COMPILE}-objcopy -O binary \
3724				 -R .note -R .comment \
3725				 -S vmlinux linux.bin
3726
3727* compress the binary image:
3728
3729	gzip -9 linux.bin
3730
3731* package compressed binary image for U-Boot:
3732
3733	mkimage -A ppc -O linux -T kernel -C gzip \
3734		-a 0 -e 0 -n "Linux Kernel Image" \
3735		-d linux.bin.gz uImage
3736
3737
3738The "mkimage" tool can also be used to create ramdisk images for use
3739with U-Boot, either separated from the Linux kernel image, or
3740combined into one file. "mkimage" encapsulates the images with a 64
3741byte header containing information about target architecture,
3742operating system, image type, compression method, entry points, time
3743stamp, CRC32 checksums, etc.
3744
3745"mkimage" can be called in two ways: to verify existing images and
3746print the header information, or to build new images.
3747
3748In the first form (with "-l" option) mkimage lists the information
3749contained in the header of an existing U-Boot image; this includes
3750checksum verification:
3751
3752	tools/mkimage -l image
3753	  -l ==> list image header information
3754
3755The second form (with "-d" option) is used to build a U-Boot image
3756from a "data file" which is used as image payload:
3757
3758	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3759		      -n name -d data_file image
3760	  -A ==> set architecture to 'arch'
3761	  -O ==> set operating system to 'os'
3762	  -T ==> set image type to 'type'
3763	  -C ==> set compression type 'comp'
3764	  -a ==> set load address to 'addr' (hex)
3765	  -e ==> set entry point to 'ep' (hex)
3766	  -n ==> set image name to 'name'
3767	  -d ==> use image data from 'datafile'
3768
3769Right now, all Linux kernels for PowerPC systems use the same load
3770address (0x00000000), but the entry point address depends on the
3771kernel version:
3772
3773- 2.2.x kernels have the entry point at 0x0000000C,
3774- 2.3.x and later kernels have the entry point at 0x00000000.
3775
3776So a typical call to build a U-Boot image would read:
3777
3778	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3779	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3780	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3781	> examples/uImage.TQM850L
3782	Image Name:   2.4.4 kernel for TQM850L
3783	Created:      Wed Jul 19 02:34:59 2000
3784	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3785	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3786	Load Address: 0x00000000
3787	Entry Point:  0x00000000
3788
3789To verify the contents of the image (or check for corruption):
3790
3791	-> tools/mkimage -l examples/uImage.TQM850L
3792	Image Name:   2.4.4 kernel for TQM850L
3793	Created:      Wed Jul 19 02:34:59 2000
3794	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3795	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3796	Load Address: 0x00000000
3797	Entry Point:  0x00000000
3798
3799NOTE: for embedded systems where boot time is critical you can trade
3800speed for memory and install an UNCOMPRESSED image instead: this
3801needs more space in Flash, but boots much faster since it does not
3802need to be uncompressed:
3803
3804	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3805	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3806	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3807	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3808	> examples/uImage.TQM850L-uncompressed
3809	Image Name:   2.4.4 kernel for TQM850L
3810	Created:      Wed Jul 19 02:34:59 2000
3811	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3812	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3813	Load Address: 0x00000000
3814	Entry Point:  0x00000000
3815
3816
3817Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3818when your kernel is intended to use an initial ramdisk:
3819
3820	-> tools/mkimage -n 'Simple Ramdisk Image' \
3821	> -A ppc -O linux -T ramdisk -C gzip \
3822	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3823	Image Name:   Simple Ramdisk Image
3824	Created:      Wed Jan 12 14:01:50 2000
3825	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
3826	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
3827	Load Address: 0x00000000
3828	Entry Point:  0x00000000
3829
3830The "dumpimage" tool can be used to disassemble or list the contents of images
3831built by mkimage. See dumpimage's help output (-h) for details.
3832
3833Installing a Linux Image:
3834-------------------------
3835
3836To downloading a U-Boot image over the serial (console) interface,
3837you must convert the image to S-Record format:
3838
3839	objcopy -I binary -O srec examples/image examples/image.srec
3840
3841The 'objcopy' does not understand the information in the U-Boot
3842image header, so the resulting S-Record file will be relative to
3843address 0x00000000. To load it to a given address, you need to
3844specify the target address as 'offset' parameter with the 'loads'
3845command.
3846
3847Example: install the image to address 0x40100000 (which on the
3848TQM8xxL is in the first Flash bank):
3849
3850	=> erase 40100000 401FFFFF
3851
3852	.......... done
3853	Erased 8 sectors
3854
3855	=> loads 40100000
3856	## Ready for S-Record download ...
3857	~>examples/image.srec
3858	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3859	...
3860	15989 15990 15991 15992
3861	[file transfer complete]
3862	[connected]
3863	## Start Addr = 0x00000000
3864
3865
3866You can check the success of the download using the 'iminfo' command;
3867this includes a checksum verification so you can be sure no data
3868corruption happened:
3869
3870	=> imi 40100000
3871
3872	## Checking Image at 40100000 ...
3873	   Image Name:	 2.2.13 for initrd on TQM850L
3874	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3875	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3876	   Load Address: 00000000
3877	   Entry Point:	 0000000c
3878	   Verifying Checksum ... OK
3879
3880
3881Boot Linux:
3882-----------
3883
3884The "bootm" command is used to boot an application that is stored in
3885memory (RAM or Flash). In case of a Linux kernel image, the contents
3886of the "bootargs" environment variable is passed to the kernel as
3887parameters. You can check and modify this variable using the
3888"printenv" and "setenv" commands:
3889
3890
3891	=> printenv bootargs
3892	bootargs=root=/dev/ram
3893
3894	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3895
3896	=> printenv bootargs
3897	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3898
3899	=> bootm 40020000
3900	## Booting Linux kernel at 40020000 ...
3901	   Image Name:	 2.2.13 for NFS on TQM850L
3902	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3903	   Data Size:	 381681 Bytes = 372 kB = 0 MB
3904	   Load Address: 00000000
3905	   Entry Point:	 0000000c
3906	   Verifying Checksum ... OK
3907	   Uncompressing Kernel Image ... OK
3908	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
3909	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3910	time_init: decrementer frequency = 187500000/60
3911	Calibrating delay loop... 49.77 BogoMIPS
3912	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3913	...
3914
3915If you want to boot a Linux kernel with initial RAM disk, you pass
3916the memory addresses of both the kernel and the initrd image (PPBCOOT
3917format!) to the "bootm" command:
3918
3919	=> imi 40100000 40200000
3920
3921	## Checking Image at 40100000 ...
3922	   Image Name:	 2.2.13 for initrd on TQM850L
3923	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3924	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3925	   Load Address: 00000000
3926	   Entry Point:	 0000000c
3927	   Verifying Checksum ... OK
3928
3929	## Checking Image at 40200000 ...
3930	   Image Name:	 Simple Ramdisk Image
3931	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3932	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3933	   Load Address: 00000000
3934	   Entry Point:	 00000000
3935	   Verifying Checksum ... OK
3936
3937	=> bootm 40100000 40200000
3938	## Booting Linux kernel at 40100000 ...
3939	   Image Name:	 2.2.13 for initrd on TQM850L
3940	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3941	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3942	   Load Address: 00000000
3943	   Entry Point:	 0000000c
3944	   Verifying Checksum ... OK
3945	   Uncompressing Kernel Image ... OK
3946	## Loading RAMDisk Image at 40200000 ...
3947	   Image Name:	 Simple Ramdisk Image
3948	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3949	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3950	   Load Address: 00000000
3951	   Entry Point:	 00000000
3952	   Verifying Checksum ... OK
3953	   Loading Ramdisk ... OK
3954	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
3955	Boot arguments: root=/dev/ram
3956	time_init: decrementer frequency = 187500000/60
3957	Calibrating delay loop... 49.77 BogoMIPS
3958	...
3959	RAMDISK: Compressed image found at block 0
3960	VFS: Mounted root (ext2 filesystem).
3961
3962	bash#
3963
3964Boot Linux and pass a flat device tree:
3965-----------
3966
3967First, U-Boot must be compiled with the appropriate defines. See the section
3968titled "Linux Kernel Interface" above for a more in depth explanation. The
3969following is an example of how to start a kernel and pass an updated
3970flat device tree:
3971
3972=> print oftaddr
3973oftaddr=0x300000
3974=> print oft
3975oft=oftrees/mpc8540ads.dtb
3976=> tftp $oftaddr $oft
3977Speed: 1000, full duplex
3978Using TSEC0 device
3979TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3980Filename 'oftrees/mpc8540ads.dtb'.
3981Load address: 0x300000
3982Loading: #
3983done
3984Bytes transferred = 4106 (100a hex)
3985=> tftp $loadaddr $bootfile
3986Speed: 1000, full duplex
3987Using TSEC0 device
3988TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3989Filename 'uImage'.
3990Load address: 0x200000
3991Loading:############
3992done
3993Bytes transferred = 1029407 (fb51f hex)
3994=> print loadaddr
3995loadaddr=200000
3996=> print oftaddr
3997oftaddr=0x300000
3998=> bootm $loadaddr - $oftaddr
3999## Booting image at 00200000 ...
4000   Image Name:	 Linux-2.6.17-dirty
4001   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4002   Data Size:	 1029343 Bytes = 1005.2 kB
4003   Load Address: 00000000
4004   Entry Point:	 00000000
4005   Verifying Checksum ... OK
4006   Uncompressing Kernel Image ... OK
4007Booting using flat device tree at 0x300000
4008Using MPC85xx ADS machine description
4009Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4010[snip]
4011
4012
4013More About U-Boot Image Types:
4014------------------------------
4015
4016U-Boot supports the following image types:
4017
4018   "Standalone Programs" are directly runnable in the environment
4019	provided by U-Boot; it is expected that (if they behave
4020	well) you can continue to work in U-Boot after return from
4021	the Standalone Program.
4022   "OS Kernel Images" are usually images of some Embedded OS which
4023	will take over control completely. Usually these programs
4024	will install their own set of exception handlers, device
4025	drivers, set up the MMU, etc. - this means, that you cannot
4026	expect to re-enter U-Boot except by resetting the CPU.
4027   "RAMDisk Images" are more or less just data blocks, and their
4028	parameters (address, size) are passed to an OS kernel that is
4029	being started.
4030   "Multi-File Images" contain several images, typically an OS
4031	(Linux) kernel image and one or more data images like
4032	RAMDisks. This construct is useful for instance when you want
4033	to boot over the network using BOOTP etc., where the boot
4034	server provides just a single image file, but you want to get
4035	for instance an OS kernel and a RAMDisk image.
4036
4037	"Multi-File Images" start with a list of image sizes, each
4038	image size (in bytes) specified by an "uint32_t" in network
4039	byte order. This list is terminated by an "(uint32_t)0".
4040	Immediately after the terminating 0 follow the images, one by
4041	one, all aligned on "uint32_t" boundaries (size rounded up to
4042	a multiple of 4 bytes).
4043
4044   "Firmware Images" are binary images containing firmware (like
4045	U-Boot or FPGA images) which usually will be programmed to
4046	flash memory.
4047
4048   "Script files" are command sequences that will be executed by
4049	U-Boot's command interpreter; this feature is especially
4050	useful when you configure U-Boot to use a real shell (hush)
4051	as command interpreter.
4052
4053Booting the Linux zImage:
4054-------------------------
4055
4056On some platforms, it's possible to boot Linux zImage. This is done
4057using the "bootz" command. The syntax of "bootz" command is the same
4058as the syntax of "bootm" command.
4059
4060Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4061kernel with raw initrd images. The syntax is slightly different, the
4062address of the initrd must be augmented by it's size, in the following
4063format: "<initrd addres>:<initrd size>".
4064
4065
4066Standalone HOWTO:
4067=================
4068
4069One of the features of U-Boot is that you can dynamically load and
4070run "standalone" applications, which can use some resources of
4071U-Boot like console I/O functions or interrupt services.
4072
4073Two simple examples are included with the sources:
4074
4075"Hello World" Demo:
4076-------------------
4077
4078'examples/hello_world.c' contains a small "Hello World" Demo
4079application; it is automatically compiled when you build U-Boot.
4080It's configured to run at address 0x00040004, so you can play with it
4081like that:
4082
4083	=> loads
4084	## Ready for S-Record download ...
4085	~>examples/hello_world.srec
4086	1 2 3 4 5 6 7 8 9 10 11 ...
4087	[file transfer complete]
4088	[connected]
4089	## Start Addr = 0x00040004
4090
4091	=> go 40004 Hello World! This is a test.
4092	## Starting application at 0x00040004 ...
4093	Hello World
4094	argc = 7
4095	argv[0] = "40004"
4096	argv[1] = "Hello"
4097	argv[2] = "World!"
4098	argv[3] = "This"
4099	argv[4] = "is"
4100	argv[5] = "a"
4101	argv[6] = "test."
4102	argv[7] = "<NULL>"
4103	Hit any key to exit ...
4104
4105	## Application terminated, rc = 0x0
4106
4107Another example, which demonstrates how to register a CPM interrupt
4108handler with the U-Boot code, can be found in 'examples/timer.c'.
4109Here, a CPM timer is set up to generate an interrupt every second.
4110The interrupt service routine is trivial, just printing a '.'
4111character, but this is just a demo program. The application can be
4112controlled by the following keys:
4113
4114	? - print current values og the CPM Timer registers
4115	b - enable interrupts and start timer
4116	e - stop timer and disable interrupts
4117	q - quit application
4118
4119	=> loads
4120	## Ready for S-Record download ...
4121	~>examples/timer.srec
4122	1 2 3 4 5 6 7 8 9 10 11 ...
4123	[file transfer complete]
4124	[connected]
4125	## Start Addr = 0x00040004
4126
4127	=> go 40004
4128	## Starting application at 0x00040004 ...
4129	TIMERS=0xfff00980
4130	Using timer 1
4131	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4132
4133Hit 'b':
4134	[q, b, e, ?] Set interval 1000000 us
4135	Enabling timer
4136Hit '?':
4137	[q, b, e, ?] ........
4138	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4139Hit '?':
4140	[q, b, e, ?] .
4141	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4142Hit '?':
4143	[q, b, e, ?] .
4144	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4145Hit '?':
4146	[q, b, e, ?] .
4147	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4148Hit 'e':
4149	[q, b, e, ?] ...Stopping timer
4150Hit 'q':
4151	[q, b, e, ?] ## Application terminated, rc = 0x0
4152
4153
4154Minicom warning:
4155================
4156
4157Over time, many people have reported problems when trying to use the
4158"minicom" terminal emulation program for serial download. I (wd)
4159consider minicom to be broken, and recommend not to use it. Under
4160Unix, I recommend to use C-Kermit for general purpose use (and
4161especially for kermit binary protocol download ("loadb" command), and
4162use "cu" for S-Record download ("loads" command).  See
4163https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4164for help with kermit.
4165
4166
4167Nevertheless, if you absolutely want to use it try adding this
4168configuration to your "File transfer protocols" section:
4169
4170	   Name	   Program			Name U/D FullScr IO-Red. Multi
4171	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4172	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4173
4174
4175NetBSD Notes:
4176=============
4177
4178Starting at version 0.9.2, U-Boot supports NetBSD both as host
4179(build U-Boot) and target system (boots NetBSD/mpc8xx).
4180
4181Building requires a cross environment; it is known to work on
4182NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4183need gmake since the Makefiles are not compatible with BSD make).
4184Note that the cross-powerpc package does not install include files;
4185attempting to build U-Boot will fail because <machine/ansi.h> is
4186missing.  This file has to be installed and patched manually:
4187
4188	# cd /usr/pkg/cross/powerpc-netbsd/include
4189	# mkdir powerpc
4190	# ln -s powerpc machine
4191	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4192	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4193
4194Native builds *don't* work due to incompatibilities between native
4195and U-Boot include files.
4196
4197Booting assumes that (the first part of) the image booted is a
4198stage-2 loader which in turn loads and then invokes the kernel
4199proper. Loader sources will eventually appear in the NetBSD source
4200tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4201meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4202
4203
4204Implementation Internals:
4205=========================
4206
4207The following is not intended to be a complete description of every
4208implementation detail. However, it should help to understand the
4209inner workings of U-Boot and make it easier to port it to custom
4210hardware.
4211
4212
4213Initial Stack, Global Data:
4214---------------------------
4215
4216The implementation of U-Boot is complicated by the fact that U-Boot
4217starts running out of ROM (flash memory), usually without access to
4218system RAM (because the memory controller is not initialized yet).
4219This means that we don't have writable Data or BSS segments, and BSS
4220is not initialized as zero. To be able to get a C environment working
4221at all, we have to allocate at least a minimal stack. Implementation
4222options for this are defined and restricted by the CPU used: Some CPU
4223models provide on-chip memory (like the IMMR area on MPC8xx and
4224MPC826x processors), on others (parts of) the data cache can be
4225locked as (mis-) used as memory, etc.
4226
4227	Chris Hallinan posted a good summary of these issues to the
4228	U-Boot mailing list:
4229
4230	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4231	From: "Chris Hallinan" <clh@net1plus.com>
4232	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4233	...
4234
4235	Correct me if I'm wrong, folks, but the way I understand it
4236	is this: Using DCACHE as initial RAM for Stack, etc, does not
4237	require any physical RAM backing up the cache. The cleverness
4238	is that the cache is being used as a temporary supply of
4239	necessary storage before the SDRAM controller is setup. It's
4240	beyond the scope of this list to explain the details, but you
4241	can see how this works by studying the cache architecture and
4242	operation in the architecture and processor-specific manuals.
4243
4244	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4245	is another option for the system designer to use as an
4246	initial stack/RAM area prior to SDRAM being available. Either
4247	option should work for you. Using CS 4 should be fine if your
4248	board designers haven't used it for something that would
4249	cause you grief during the initial boot! It is frequently not
4250	used.
4251
4252	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4253	with your processor/board/system design. The default value
4254	you will find in any recent u-boot distribution in
4255	walnut.h should work for you. I'd set it to a value larger
4256	than your SDRAM module. If you have a 64MB SDRAM module, set
4257	it above 400_0000. Just make sure your board has no resources
4258	that are supposed to respond to that address! That code in
4259	start.S has been around a while and should work as is when
4260	you get the config right.
4261
4262	-Chris Hallinan
4263	DS4.COM, Inc.
4264
4265It is essential to remember this, since it has some impact on the C
4266code for the initialization procedures:
4267
4268* Initialized global data (data segment) is read-only. Do not attempt
4269  to write it.
4270
4271* Do not use any uninitialized global data (or implicitly initialized
4272  as zero data - BSS segment) at all - this is undefined, initiali-
4273  zation is performed later (when relocating to RAM).
4274
4275* Stack space is very limited. Avoid big data buffers or things like
4276  that.
4277
4278Having only the stack as writable memory limits means we cannot use
4279normal global data to share information between the code. But it
4280turned out that the implementation of U-Boot can be greatly
4281simplified by making a global data structure (gd_t) available to all
4282functions. We could pass a pointer to this data as argument to _all_
4283functions, but this would bloat the code. Instead we use a feature of
4284the GCC compiler (Global Register Variables) to share the data: we
4285place a pointer (gd) to the global data into a register which we
4286reserve for this purpose.
4287
4288When choosing a register for such a purpose we are restricted by the
4289relevant  (E)ABI  specifications for the current architecture, and by
4290GCC's implementation.
4291
4292For PowerPC, the following registers have specific use:
4293	R1:	stack pointer
4294	R2:	reserved for system use
4295	R3-R4:	parameter passing and return values
4296	R5-R10: parameter passing
4297	R13:	small data area pointer
4298	R30:	GOT pointer
4299	R31:	frame pointer
4300
4301	(U-Boot also uses R12 as internal GOT pointer. r12
4302	is a volatile register so r12 needs to be reset when
4303	going back and forth between asm and C)
4304
4305    ==> U-Boot will use R2 to hold a pointer to the global data
4306
4307    Note: on PPC, we could use a static initializer (since the
4308    address of the global data structure is known at compile time),
4309    but it turned out that reserving a register results in somewhat
4310    smaller code - although the code savings are not that big (on
4311    average for all boards 752 bytes for the whole U-Boot image,
4312    624 text + 127 data).
4313
4314On ARM, the following registers are used:
4315
4316	R0:	function argument word/integer result
4317	R1-R3:	function argument word
4318	R9:	platform specific
4319	R10:	stack limit (used only if stack checking is enabled)
4320	R11:	argument (frame) pointer
4321	R12:	temporary workspace
4322	R13:	stack pointer
4323	R14:	link register
4324	R15:	program counter
4325
4326    ==> U-Boot will use R9 to hold a pointer to the global data
4327
4328    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4329
4330On Nios II, the ABI is documented here:
4331	https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4332
4333    ==> U-Boot will use gp to hold a pointer to the global data
4334
4335    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4336    to access small data sections, so gp is free.
4337
4338On NDS32, the following registers are used:
4339
4340	R0-R1:	argument/return
4341	R2-R5:	argument
4342	R15:	temporary register for assembler
4343	R16:	trampoline register
4344	R28:	frame pointer (FP)
4345	R29:	global pointer (GP)
4346	R30:	link register (LP)
4347	R31:	stack pointer (SP)
4348	PC:	program counter (PC)
4349
4350    ==> U-Boot will use R10 to hold a pointer to the global data
4351
4352NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4353or current versions of GCC may "optimize" the code too much.
4354
4355On RISC-V, the following registers are used:
4356
4357	x0: hard-wired zero (zero)
4358	x1: return address (ra)
4359	x2:	stack pointer (sp)
4360	x3:	global pointer (gp)
4361	x4:	thread pointer (tp)
4362	x5:	link register (t0)
4363	x8:	frame pointer (fp)
4364	x10-x11:	arguments/return values (a0-1)
4365	x12-x17:	arguments (a2-7)
4366	x28-31:	 temporaries (t3-6)
4367	pc:	program counter (pc)
4368
4369    ==> U-Boot will use gp to hold a pointer to the global data
4370
4371Memory Management:
4372------------------
4373
4374U-Boot runs in system state and uses physical addresses, i.e. the
4375MMU is not used either for address mapping nor for memory protection.
4376
4377The available memory is mapped to fixed addresses using the memory
4378controller. In this process, a contiguous block is formed for each
4379memory type (Flash, SDRAM, SRAM), even when it consists of several
4380physical memory banks.
4381
4382U-Boot is installed in the first 128 kB of the first Flash bank (on
4383TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4384booting and sizing and initializing DRAM, the code relocates itself
4385to the upper end of DRAM. Immediately below the U-Boot code some
4386memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4387configuration setting]. Below that, a structure with global Board
4388Info data is placed, followed by the stack (growing downward).
4389
4390Additionally, some exception handler code is copied to the low 8 kB
4391of DRAM (0x00000000 ... 0x00001FFF).
4392
4393So a typical memory configuration with 16 MB of DRAM could look like
4394this:
4395
4396	0x0000 0000	Exception Vector code
4397	      :
4398	0x0000 1FFF
4399	0x0000 2000	Free for Application Use
4400	      :
4401	      :
4402
4403	      :
4404	      :
4405	0x00FB FF20	Monitor Stack (Growing downward)
4406	0x00FB FFAC	Board Info Data and permanent copy of global data
4407	0x00FC 0000	Malloc Arena
4408	      :
4409	0x00FD FFFF
4410	0x00FE 0000	RAM Copy of Monitor Code
4411	...		eventually: LCD or video framebuffer
4412	...		eventually: pRAM (Protected RAM - unchanged by reset)
4413	0x00FF FFFF	[End of RAM]
4414
4415
4416System Initialization:
4417----------------------
4418
4419In the reset configuration, U-Boot starts at the reset entry point
4420(on most PowerPC systems at address 0x00000100). Because of the reset
4421configuration for CS0# this is a mirror of the on board Flash memory.
4422To be able to re-map memory U-Boot then jumps to its link address.
4423To be able to implement the initialization code in C, a (small!)
4424initial stack is set up in the internal Dual Ported RAM (in case CPUs
4425which provide such a feature like), or in a locked part of the data
4426cache. After that, U-Boot initializes the CPU core, the caches and
4427the SIU.
4428
4429Next, all (potentially) available memory banks are mapped using a
4430preliminary mapping. For example, we put them on 512 MB boundaries
4431(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4432on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4433programmed for SDRAM access. Using the temporary configuration, a
4434simple memory test is run that determines the size of the SDRAM
4435banks.
4436
4437When there is more than one SDRAM bank, and the banks are of
4438different size, the largest is mapped first. For equal size, the first
4439bank (CS2#) is mapped first. The first mapping is always for address
44400x00000000, with any additional banks following immediately to create
4441contiguous memory starting from 0.
4442
4443Then, the monitor installs itself at the upper end of the SDRAM area
4444and allocates memory for use by malloc() and for the global Board
4445Info data; also, the exception vector code is copied to the low RAM
4446pages, and the final stack is set up.
4447
4448Only after this relocation will you have a "normal" C environment;
4449until that you are restricted in several ways, mostly because you are
4450running from ROM, and because the code will have to be relocated to a
4451new address in RAM.
4452
4453
4454U-Boot Porting Guide:
4455----------------------
4456
4457[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4458list, October 2002]
4459
4460
4461int main(int argc, char *argv[])
4462{
4463	sighandler_t no_more_time;
4464
4465	signal(SIGALRM, no_more_time);
4466	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4467
4468	if (available_money > available_manpower) {
4469		Pay consultant to port U-Boot;
4470		return 0;
4471	}
4472
4473	Download latest U-Boot source;
4474
4475	Subscribe to u-boot mailing list;
4476
4477	if (clueless)
4478		email("Hi, I am new to U-Boot, how do I get started?");
4479
4480	while (learning) {
4481		Read the README file in the top level directory;
4482		Read https://www.denx.de/wiki/bin/view/DULG/Manual;
4483		Read applicable doc/README.*;
4484		Read the source, Luke;
4485		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4486	}
4487
4488	if (available_money > toLocalCurrency ($2500))
4489		Buy a BDI3000;
4490	else
4491		Add a lot of aggravation and time;
4492
4493	if (a similar board exists) {	/* hopefully... */
4494		cp -a board/<similar> board/<myboard>
4495		cp include/configs/<similar>.h include/configs/<myboard>.h
4496	} else {
4497		Create your own board support subdirectory;
4498		Create your own board include/configs/<myboard>.h file;
4499	}
4500	Edit new board/<myboard> files
4501	Edit new include/configs/<myboard>.h
4502
4503	while (!accepted) {
4504		while (!running) {
4505			do {
4506				Add / modify source code;
4507			} until (compiles);
4508			Debug;
4509			if (clueless)
4510				email("Hi, I am having problems...");
4511		}
4512		Send patch file to the U-Boot email list;
4513		if (reasonable critiques)
4514			Incorporate improvements from email list code review;
4515		else
4516			Defend code as written;
4517	}
4518
4519	return 0;
4520}
4521
4522void no_more_time (int sig)
4523{
4524      hire_a_guru();
4525}
4526
4527
4528Coding Standards:
4529-----------------
4530
4531All contributions to U-Boot should conform to the Linux kernel
4532coding style; see the kernel coding style guide at
4533https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4534script "scripts/Lindent" in your Linux kernel source directory.
4535
4536Source files originating from a different project (for example the
4537MTD subsystem) are generally exempt from these guidelines and are not
4538reformatted to ease subsequent migration to newer versions of those
4539sources.
4540
4541Please note that U-Boot is implemented in C (and to some small parts in
4542Assembler); no C++ is used, so please do not use C++ style comments (//)
4543in your code.
4544
4545Please also stick to the following formatting rules:
4546- remove any trailing white space
4547- use TAB characters for indentation and vertical alignment, not spaces
4548- make sure NOT to use DOS '\r\n' line feeds
4549- do not add more than 2 consecutive empty lines to source files
4550- do not add trailing empty lines to source files
4551
4552Submissions which do not conform to the standards may be returned
4553with a request to reformat the changes.
4554
4555
4556Submitting Patches:
4557-------------------
4558
4559Since the number of patches for U-Boot is growing, we need to
4560establish some rules. Submissions which do not conform to these rules
4561may be rejected, even when they contain important and valuable stuff.
4562
4563Please see https://www.denx.de/wiki/U-Boot/Patches for details.
4564
4565Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4566see https://lists.denx.de/listinfo/u-boot
4567
4568When you send a patch, please include the following information with
4569it:
4570
4571* For bug fixes: a description of the bug and how your patch fixes
4572  this bug. Please try to include a way of demonstrating that the
4573  patch actually fixes something.
4574
4575* For new features: a description of the feature and your
4576  implementation.
4577
4578* For major contributions, add a MAINTAINERS file with your
4579  information and associated file and directory references.
4580
4581* When you add support for a new board, don't forget to add a
4582  maintainer e-mail address to the boards.cfg file, too.
4583
4584* If your patch adds new configuration options, don't forget to
4585  document these in the README file.
4586
4587* The patch itself. If you are using git (which is *strongly*
4588  recommended) you can easily generate the patch using the
4589  "git format-patch". If you then use "git send-email" to send it to
4590  the U-Boot mailing list, you will avoid most of the common problems
4591  with some other mail clients.
4592
4593  If you cannot use git, use "diff -purN OLD NEW". If your version of
4594  diff does not support these options, then get the latest version of
4595  GNU diff.
4596
4597  The current directory when running this command shall be the parent
4598  directory of the U-Boot source tree (i. e. please make sure that
4599  your patch includes sufficient directory information for the
4600  affected files).
4601
4602  We prefer patches as plain text. MIME attachments are discouraged,
4603  and compressed attachments must not be used.
4604
4605* If one logical set of modifications affects or creates several
4606  files, all these changes shall be submitted in a SINGLE patch file.
4607
4608* Changesets that contain different, unrelated modifications shall be
4609  submitted as SEPARATE patches, one patch per changeset.
4610
4611
4612Notes:
4613
4614* Before sending the patch, run the buildman script on your patched
4615  source tree and make sure that no errors or warnings are reported
4616  for any of the boards.
4617
4618* Keep your modifications to the necessary minimum: A patch
4619  containing several unrelated changes or arbitrary reformats will be
4620  returned with a request to re-formatting / split it.
4621
4622* If you modify existing code, make sure that your new code does not
4623  add to the memory footprint of the code ;-) Small is beautiful!
4624  When adding new features, these should compile conditionally only
4625  (using #ifdef), and the resulting code with the new feature
4626  disabled must not need more memory than the old code without your
4627  modification.
4628
4629* Remember that there is a size limit of 100 kB per message on the
4630  u-boot mailing list. Bigger patches will be moderated. If they are
4631  reasonable and not too big, they will be acknowledged. But patches
4632  bigger than the size limit should be avoided.
4633