1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Driver for LM70EVAL-LLP board for the LM70 sensor 4 * 5 * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com> 6 */ 7 8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 9 10 #include <linux/init.h> 11 #include <linux/module.h> 12 #include <linux/kernel.h> 13 #include <linux/delay.h> 14 #include <linux/device.h> 15 #include <linux/parport.h> 16 #include <linux/sysfs.h> 17 #include <linux/workqueue.h> 18 19 #include <linux/spi/spi.h> 20 #include <linux/spi/spi_bitbang.h> 21 22 /* 23 * The LM70 communicates with a host processor using a 3-wire variant of 24 * the SPI/Microwire bus interface. This driver specifically supports an 25 * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel 26 * port to bitbang an SPI-parport bridge. Accordingly, this is an SPI 27 * host controller driver. The hwmon/lm70 driver is a "SPI protocol 28 * driver", layered on top of this one and usable without the lm70llp. 29 * 30 * Datasheet and Schematic: 31 * The LM70 is a temperature sensor chip from National Semiconductor; its 32 * datasheet is available at https://www.ti.com/lit/gpn/lm70 33 * The schematic for this particular board (the LM70EVAL-LLP) is 34 * available (on page 4) here: 35 * https://download.datasheets.com/pdfs/documentation/nat/kit&board/lm70llpevalmanual.pdf 36 * 37 * Also see Documentation/spi/spi-lm70llp.rst. The SPI<->parport code here is 38 * (heavily) based on spi-butterfly by David Brownell. 39 * 40 * The LM70 LLP connects to the PC parallel port in the following manner: 41 * 42 * Parallel LM70 LLP 43 * Port Direction JP2 Header 44 * ----------- --------- ------------ 45 * D0 2 - - 46 * D1 3 --> V+ 5 47 * D2 4 --> V+ 5 48 * D3 5 --> V+ 5 49 * D4 6 --> V+ 5 50 * D5 7 --> nCS 8 51 * D6 8 --> SCLK 3 52 * D7 9 --> SI/O 5 53 * GND 25 - GND 7 54 * Select 13 <-- SI/O 1 55 * 56 * Note that parport pin 13 actually gets inverted by the transistor 57 * arrangement which lets either the parport or the LM70 drive the 58 * SI/SO signal (see the schematic for details). 59 */ 60 61 #define DRVNAME "spi-lm70llp" 62 63 #define lm70_INIT 0xBE 64 #define SIO 0x10 65 #define nCS 0x20 66 #define SCLK 0x40 67 68 /*-------------------------------------------------------------------------*/ 69 70 struct spi_lm70llp { 71 struct spi_bitbang bitbang; 72 struct parport *port; 73 struct pardevice *pd; 74 struct spi_device *spidev_lm70; 75 struct spi_board_info info; 76 //struct device *dev; 77 }; 78 79 /* REVISIT : ugly global ; provides "exclusive open" facility */ 80 static struct spi_lm70llp *lm70llp; 81 82 /*-------------------------------------------------------------------*/ 83 84 static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi) 85 { 86 return spi->controller_data; 87 } 88 89 /*---------------------- LM70 LLP eval board-specific inlines follow */ 90 91 /* NOTE: we don't actually need to reread the output values, since they'll 92 * still be what we wrote before. Plus, going through parport builds in 93 * a ~1ms/operation delay; these SPI transfers could easily be faster. 94 */ 95 96 static inline void deassertCS(struct spi_lm70llp *pp) 97 { 98 u8 data = parport_read_data(pp->port); 99 100 data &= ~0x80; /* pull D7/SI-out low while de-asserted */ 101 parport_write_data(pp->port, data | nCS); 102 } 103 104 static inline void assertCS(struct spi_lm70llp *pp) 105 { 106 u8 data = parport_read_data(pp->port); 107 108 data |= 0x80; /* pull D7/SI-out high so lm70 drives SO-in */ 109 parport_write_data(pp->port, data & ~nCS); 110 } 111 112 static inline void clkHigh(struct spi_lm70llp *pp) 113 { 114 u8 data = parport_read_data(pp->port); 115 116 parport_write_data(pp->port, data | SCLK); 117 } 118 119 static inline void clkLow(struct spi_lm70llp *pp) 120 { 121 u8 data = parport_read_data(pp->port); 122 123 parport_write_data(pp->port, data & ~SCLK); 124 } 125 126 /*------------------------- SPI-LM70-specific inlines ----------------------*/ 127 128 static inline void spidelay(unsigned d) 129 { 130 udelay(d); 131 } 132 133 static inline void setsck(struct spi_device *s, int is_on) 134 { 135 struct spi_lm70llp *pp = spidev_to_pp(s); 136 137 if (is_on) 138 clkHigh(pp); 139 else 140 clkLow(pp); 141 } 142 143 static inline void setmosi(struct spi_device *s, int is_on) 144 { 145 /* FIXME update D7 ... this way we can put the chip 146 * into shutdown mode and read the manufacturer ID, 147 * but we can't put it back into operational mode. 148 */ 149 } 150 151 /* 152 * getmiso: 153 * Why do we return 0 when the SIO line is high and vice-versa? 154 * The fact is, the lm70 eval board from NS (which this driver drives), 155 * is wired in just such a way : when the lm70's SIO goes high, a transistor 156 * switches it to low reflecting this on the parport (pin 13), and vice-versa. 157 */ 158 static inline int getmiso(struct spi_device *s) 159 { 160 struct spi_lm70llp *pp = spidev_to_pp(s); 161 162 return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1); 163 } 164 165 /*--------------------------------------------------------------------*/ 166 167 #include "spi-bitbang-txrx.h" 168 169 static void lm70_chipselect(struct spi_device *spi, int value) 170 { 171 struct spi_lm70llp *pp = spidev_to_pp(spi); 172 173 if (value) 174 assertCS(pp); 175 else 176 deassertCS(pp); 177 } 178 179 /* 180 * Our actual bitbanger routine. 181 */ 182 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits, 183 unsigned flags) 184 { 185 return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); 186 } 187 188 static void spi_lm70llp_attach(struct parport *p) 189 { 190 struct pardevice *pd; 191 struct spi_lm70llp *pp; 192 struct spi_controller *host; 193 int status; 194 struct pardev_cb lm70llp_cb; 195 196 if (lm70llp) { 197 pr_warn("spi_lm70llp instance already loaded. Aborting.\n"); 198 return; 199 } 200 201 /* TODO: this just _assumes_ a lm70 is there ... no probe; 202 * the lm70 driver could verify it, reading the manf ID. 203 */ 204 205 host = spi_alloc_host(p->physport->dev, sizeof(*pp)); 206 if (!host) { 207 status = -ENOMEM; 208 goto out_fail; 209 } 210 pp = spi_controller_get_devdata(host); 211 212 /* 213 * SPI and bitbang hookup. 214 */ 215 pp->bitbang.ctlr = host; 216 pp->bitbang.chipselect = lm70_chipselect; 217 pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx; 218 pp->bitbang.flags = SPI_3WIRE; 219 220 /* 221 * Parport hookup 222 */ 223 pp->port = p; 224 memset(&lm70llp_cb, 0, sizeof(lm70llp_cb)); 225 lm70llp_cb.private = pp; 226 lm70llp_cb.flags = PARPORT_FLAG_EXCL; 227 pd = parport_register_dev_model(p, DRVNAME, &lm70llp_cb, 0); 228 229 if (!pd) { 230 status = -ENOMEM; 231 goto out_free_host; 232 } 233 pp->pd = pd; 234 235 status = parport_claim(pd); 236 if (status < 0) 237 goto out_parport_unreg; 238 239 /* 240 * Start SPI ... 241 */ 242 status = spi_bitbang_start(&pp->bitbang); 243 if (status < 0) { 244 dev_warn(&pd->dev, "spi_bitbang_start failed with status %d\n", 245 status); 246 goto out_off_and_release; 247 } 248 249 /* 250 * The modalias name MUST match the device_driver name 251 * for the bus glue code to match and subsequently bind them. 252 * We are binding to the generic drivers/hwmon/lm70.c device 253 * driver. 254 */ 255 strcpy(pp->info.modalias, "lm70"); 256 pp->info.max_speed_hz = 6 * 1000 * 1000; 257 pp->info.chip_select = 0; 258 pp->info.mode = SPI_3WIRE | SPI_MODE_0; 259 260 /* power up the chip, and let the LM70 control SI/SO */ 261 parport_write_data(pp->port, lm70_INIT); 262 263 /* Enable access to our primary data structure via 264 * the board info's (void *)controller_data. 265 */ 266 pp->info.controller_data = pp; 267 pp->spidev_lm70 = spi_new_device(pp->bitbang.ctlr, &pp->info); 268 if (pp->spidev_lm70) 269 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n", 270 dev_name(&pp->spidev_lm70->dev)); 271 else { 272 dev_warn(&pd->dev, "spi_new_device failed\n"); 273 status = -ENODEV; 274 goto out_bitbang_stop; 275 } 276 pp->spidev_lm70->bits_per_word = 8; 277 278 lm70llp = pp; 279 return; 280 281 out_bitbang_stop: 282 spi_bitbang_stop(&pp->bitbang); 283 out_off_and_release: 284 /* power down */ 285 parport_write_data(pp->port, 0); 286 mdelay(10); 287 parport_release(pp->pd); 288 out_parport_unreg: 289 parport_unregister_device(pd); 290 out_free_host: 291 spi_controller_put(host); 292 out_fail: 293 pr_info("spi_lm70llp probe fail, status %d\n", status); 294 } 295 296 static void spi_lm70llp_detach(struct parport *p) 297 { 298 struct spi_lm70llp *pp; 299 300 if (!lm70llp || lm70llp->port != p) 301 return; 302 303 pp = lm70llp; 304 spi_bitbang_stop(&pp->bitbang); 305 306 /* power down */ 307 parport_write_data(pp->port, 0); 308 309 parport_release(pp->pd); 310 parport_unregister_device(pp->pd); 311 312 spi_controller_put(pp->bitbang.ctlr); 313 314 lm70llp = NULL; 315 } 316 317 static struct parport_driver spi_lm70llp_drv = { 318 .name = DRVNAME, 319 .match_port = spi_lm70llp_attach, 320 .detach = spi_lm70llp_detach, 321 .devmodel = true, 322 }; 323 module_parport_driver(spi_lm70llp_drv); 324 325 MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>"); 326 MODULE_DESCRIPTION( 327 "Parport adapter for the National Semiconductor LM70 LLP eval board"); 328 MODULE_LICENSE("GPL"); 329