xref: /netbsd/sys/dev/ic/README.ncr5380sbc (revision bf9ec67e)
1NCR 53C80/53C400 driver
2
3BACKGROUND
4----------
5The NCR 53C80 SCSI Bus Controller (SBC) is an early single-chip solution
6which formed the basis of many early SCSI host adapters for both the
7i386 and m68k platforms. The NCR 53C400 is a slightly more advanced
8chip which retains backward compatibility with the 53C80.
9
10On the PC, the NCR 53C80 was most commonly used to implement simple, cheap
11SCSI host adapters that were bundled with tape and CD-ROM drives. Since
12these controllers were not bus-mastering (and in some cases were not even
13interrupt-driven), they (like IDE adapters) required the CPU to perform
14much of the actual processing. These days, these controllers are cheap
15and plentiful since many are not supported by Windows 95.
16
17Similarly, NetBSD, although it has had an MI 53C80 driver (used by the
18Sun3 and Mac68k ports) for some time, has not had a i386 driver.
19
20Until now, that is...
21
22OVERVIEW
23--------
24The NCR 53C80/53C400 driver (the 'nca' device) consists of two pieces:
25
26	1) Patches for the 53C80 MI driver to make it use bus_space()
27	   functions. (This requires an optional define. By default,
28	   the driver will compile in "legacy" memory-mapped mode.
29
30	2) A machine-dependent driver (nca) containing probe and
31	   attachment routines.
32
33This driver has bene tested with the following adapters:
34
35	NCS-250 (Chinon)	53C80, port-mapped, polled-mode
36				(This is used in my primary development
37				box to drive an external Zip drive.)
38	Sumo SCSI-AT		53C80, port-mapped, interrupt driven
39				(Note: This is an odd card in that its
40				own firmware seems to have trouble detecting
41				attached drives. Under NetBSD, however,
42				it operates with no problems.)
43	Trantor T-160		53C400, port-mapped, interrupt driven
44				This card was often bundled with NEC
45				CD-ROM drives. (My standalone test box
46				is using this as its primary adapter.)
47	DTC 3150V		53C400, memory-mapped, interrupt driven
48				This a simple card designed to drive
49				a CD-ROM.
50
51CONFIGURATION
52-------------
53To setup the nca driver, the configuration file must contain the following:
54
55	options	NCR5380_USE_BUS_SPACE
56
57This line is required to add bus_space() compatibility to the MI driver.
58
59Next you need to add one or more configuration lines for the nca devices:
60
61	nca0	at isa? port 0x360 irq 15
62	nca1	at isa? iomem 0xd8000 irq 5
63
64The first is for a port-mapped controller at 0x360, IRQ 15. The second line
65is for a memory-mapped controller (Trantor T128 or equivalent) at
660xd800-0xdff, IRQ 5.
67
68You can also set up the driver in "polled" mode (i.e., no interrupts) by
69leaving off the "irq" portion of the line:
70
71	nca0	at isa? port 0x360
72	nca1	at isa? iomem 0xd8000
73
74Lastly, you need to add a scsibus attachment line for the nca device:
75
76	scsibus* at nca?
77
78The following is the probe output from my test system:
79
80	Copyright (c) 1996, 1997, 1998
81	    The NetBSD Foundation, Inc.  All rights reserved.
82	Copyright (c) 1982, 1986, 1989, 1991, 1993
83	    The Regents of the University of California.  All rights reserved.
84
85	NetBSD 1.3.2 (GENERIC) #2: Sun Oct  4 17:11:43 EDT 1998
86	    root@hefalump:/usr/src/sys/arch/i386/compile/GENERIC
87	cpu0: Intel 486DX (486-class)
88	real mem  = 7995392
89	avail mem = 5349376
90	using 123 buffers containing 503808 bytes of memory
91	mainbus0 (root)
92	isa0 at mainbus0
93	com1 at isa0 port 0x2f8-0x2ff irq 3: ns8250 or ns16450, no fifo
94	com2 at isa0 port 0x3e8-0x3ef irq 5: ns8250 or ns16450, no fifo
95	lpt0 at isa0 port 0x378-0x37b irq 7
96	nca0 at isa0 port 0x360-0x36f irq 15
97	nca0: NCR 53C400 detected
98	scsibus0 at nca0: 8 targets
99	sd0 at scsibus0 targ 0 lun 0: <HP, C2235, 0B11> SCSI2 0/direct fixed
100	sd0: 402MB, 1574 cyl, 9 head, 58 sec, 512 bytes/sect x 825012 sectors
101	cd0 at scsibus0 targ 6 lun 0: <CHINON, CD-ROM CDS-535, Q20> SCSI2 5/cdrom removable
102	nca1 at isa0 iomem 0xdb878-0xdb887 irq 5
103	nca1: NCR 53C400 detected
104	scsibus1 at nca1: 8 targets
105	sd1 at scsibus1 targ 5 lun 0: <IOMEGA, ZIP 100, J.02> SCSI2 0/direct removable
106	sd1: 96MB, 96 cyl, 64 head, 32 sec, 512 bytes/sect x 196608 sectors
107	npx0 at isa0 port 0xf0-0xff: using exception 16
108	pc0 at isa0 port 0x60-0x6f irq 1: color
109	pc0: console
110	fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
111	fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
112	biomask 8060 netmask 8460 ttymask 84e2
113	boot device: sd0
114	root on sd0a dumps on sd0b
115	root file system type: ffs
116
117In this output, nca0 is a Trantor T-160 and nca1 is a DTC 3150V. Both happen
118to be 53C400-based controllers.
119
120LIMITATIONS
121-----------
122As of this writing, the nca driver has two known limitations:
123
1241) No DMA or pseudo-DMA support
125
126This is unfortunate, but may be remedied in a later release. I would welcome
127any help by someone more familiar with DMA, particularly in relation to
128bus_space().
129
130As it is, however, performance of the nca driver is acceptable, though some
131of that may depend on one's definition of "acceptable". Remember that these
132were not high speed controller under the best conditions, so much of it is
133really the nature of the beast. It should be adequate for tapes, CD-ROMS,
134and low-usage disk devices (e.g., Zip drives). If you want to drive a CD-R
135drive, then invest in an Adaptec 154X or a PCI controller.
136
1372) No support for the SCSI port of the Pro AudioStudio 16.
138
139This is also unfortunate and may not be able to be remedied withing the
140current framework of the bus_space() functions and the nca driver.
141
142The problem is this: In most adapters, the eight 53C80 registers are mapped
143to eight sequential locations, either ports or memory addresses. On the
144PAS-16, however, the registers are mapped to two sets of ports- four
145sequential ports at the base address and four sequential ports located
1460x2000 higher. As I currently understand it, this is not supportable by
147the current bus_space() implementation nor is it possible for the driver
148to allocate a second bus_space_tag and _handle itself to accomodate the
149second set of ports. Without either, it is very difficult to imagine how
150a portable linkage to the MI driver could be made.
151
152Again, I welcome suggestions.
153
154HISTORY
155-------
156An nca driver first appeared in FreeBSD.
157
158This particular one borrows a little code from it and some from the i386
159'esp' and sun3 'si' drivers. It, like many things in the free unix world,
160was written because it solved a problem- mine! In my case, it was a need
161of a SCSI card and a lack of IRQs. The good news was that I had one
162(NCS-250); the bad news was that it was not supported under NetBSD. The
163rest is history.
164
165DISCLAIMER
166----------
167Like most things, you should take this code with a grain of salt. I have
168tried to test it sufficiently, but it is always possible that it is not
169compatible with some aspect of your system. If you end up suffering
170massive data loss and destruction, you have my sympathies, but I do not
171and will not allow myself to be held responsible.
172
173CREDITS
174-------
175My thanks to Jason Thorpe and the rest of the NetBSD team for making it
176so easy to write this driver. My thanks also to the authors of the
177FreeBSD nca driver for inspiration and 53C400 support.
178
179In the end, I hope that someone else can find this driver as useful as I
180have. If so, please drop me a line at jruschme@exit109.com and let me
181know about it.
182
183Share and enjoy
184
185John Ruschmeyer (jruschme@exit109.com)
18611 October 1998
187