drivers/spi/spi-lm70llp.c

   1 /*
   2  * Driver for LM70EVAL-LLP board for the LM70 sensor
   3  *
   4  * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18
  19 #include <linux/init.h>
  20 #include <linux/module.h>
  21 #include <linux/kernel.h>
  22 #include <linux/delay.h>
  23 #include <linux/device.h>
  24 #include <linux/parport.h>
  25 #include <linux/sysfs.h>
  26 #include <linux/workqueue.h>
  27
  28 #include <linux/spi/spi.h>
  29 #include <linux/spi/spi_bitbang.h>
  30
  31 /*
  32  * The LM70 communicates with a host processor using a 3-wire variant of
  33  * the SPI/Microwire bus interface. This driver specifically supports an
  34  * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
  35  * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
  36  * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
  37  * driver", layered on top of this one and usable without the lm70llp.
  38  *
  39  * Datasheet and Schematic:
  40  * The LM70 is a temperature sensor chip from National Semiconductor; its
  41  * datasheet is available at http://www.national.com/pf/LM/LM70.html
  42  * The schematic for this particular board (the LM70EVAL-LLP) is
  43  * available (on page 4) here:
  44  *  http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
  45  *
  46  * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
  47  * (heavily) based on spi-butterfly by David Brownell.
  48  *
  49  * The LM70 LLP connects to the PC parallel port in the following manner:
  50  *
  51  *   Parallel                 LM70 LLP
  52  *     Port      Direction   JP2 Header
  53  *  -----------  ---------  ------------
  54  *      D0    2      -         -
  55  *      D1    3     -->      V+   5
  56  *      D2    4     -->      V+   5
  57  *      D3    5     -->      V+   5
  58  *      D4    6     -->      V+   5
  59  *      D5    7     -->      nCS  8
  60  *      D6    8     -->      SCLK 3
  61  *      D7    9     -->      SI/O 5
  62  *     GND   25      -       GND  7
  63  *    Select 13     <--      SI/O 1
  64  *
  65  * Note that parport pin 13 actually gets inverted by the transistor
  66  * arrangement which lets either the parport or the LM70 drive the
  67  * SI/SO signal (see the schematic for details).
  68  */
  69
  70 #define DRVNAME         "spi-lm70llp"
  71
  72 #define lm70_INIT       0xBE
  73 #define SIO             0x10
  74 #define nCS             0x20
  75 #define SCLK            0x40
  76
  77 /*-------------------------------------------------------------------------*/
  78
  79 struct spi_lm70llp {
  80         struct spi_bitbang      bitbang;
  81         struct parport          *port;
  82         struct pardevice        *pd;
  83         struct spi_device       *spidev_lm70;
  84         struct spi_board_info   info;
  85         //struct device         *dev;
  86 };
  87
  88 /* REVISIT : ugly global ; provides "exclusive open" facility */
  89 static struct spi_lm70llp *lm70llp;
  90
  91 /*-------------------------------------------------------------------*/
  92
  93 static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
  94 {
  95         return spi->controller_data;
  96 }
  97
  98 /*---------------------- LM70 LLP eval board-specific inlines follow */
  99
 100 /* NOTE:  we don't actually need to reread the output values, since they'll
 101  * still be what we wrote before.  Plus, going through parport builds in
 102  * a ~1ms/operation delay; these SPI transfers could easily be faster.
 103  */
 104
 105 static inline void deassertCS(struct spi_lm70llp *pp)
 106 {
 107         u8 data = parport_read_data(pp->port);
 108
 109         data &= ~0x80;          /* pull D7/SI-out low while de-asserted */
 110         parport_write_data(pp->port, data | nCS);
 111 }
 112
 113 static inline void assertCS(struct spi_lm70llp *pp)
 114 {
 115         u8 data = parport_read_data(pp->port);
 116
 117         data |= 0x80;           /* pull D7/SI-out high so lm70 drives SO-in */
 118         parport_write_data(pp->port, data & ~nCS);
 119 }
 120
 121 static inline void clkHigh(struct spi_lm70llp *pp)
 122 {
 123         u8 data = parport_read_data(pp->port);
 124
 125         parport_write_data(pp->port, data | SCLK);
 126 }
 127
 128 static inline void clkLow(struct spi_lm70llp *pp)
 129 {
 130         u8 data = parport_read_data(pp->port);
 131
 132         parport_write_data(pp->port, data & ~SCLK);
 133 }
 134
 135 /*------------------------- SPI-LM70-specific inlines ----------------------*/
 136
 137 static inline void spidelay(unsigned d)
 138 {
 139         udelay(d);
 140 }
 141
 142 static inline void setsck(struct spi_device *s, int is_on)
 143 {
 144         struct spi_lm70llp *pp = spidev_to_pp(s);
 145
 146         if (is_on)
 147                 clkHigh(pp);
 148         else
 149                 clkLow(pp);
 150 }
 151
 152 static inline void setmosi(struct spi_device *s, int is_on)
 153 {
 154         /* FIXME update D7 ... this way we can put the chip
 155          * into shutdown mode and read the manufacturer ID,
 156          * but we can't put it back into operational mode.
 157          */
 158 }
 159
 160 /*
 161  * getmiso:
 162  * Why do we return 0 when the SIO line is high and vice-versa?
 163  * The fact is, the lm70 eval board from NS (which this driver drives),
 164  * is wired in just such a way : when the lm70's SIO goes high, a transistor
 165  * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 166  */
 167 static inline int getmiso(struct spi_device *s)
 168 {
 169         struct spi_lm70llp *pp = spidev_to_pp(s);
 170
 171         return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1);
 172 }
 173
 174 /*--------------------------------------------------------------------*/
 175
 176 #include "spi-bitbang-txrx.h"
 177
 178 static void lm70_chipselect(struct spi_device *spi, int value)
 179 {
 180         struct spi_lm70llp *pp = spidev_to_pp(spi);
 181
 182         if (value)
 183                 assertCS(pp);
 184         else
 185                 deassertCS(pp);
 186 }
 187
 188 /*
 189  * Our actual bitbanger routine.
 190  */
 191 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits,
 192                      unsigned flags)
 193 {
 194         return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
 195 }
 196
 197 static void spi_lm70llp_attach(struct parport *p)
 198 {
 199         struct pardevice        *pd;
 200         struct spi_lm70llp      *pp;
 201         struct spi_master       *master;
 202         int                     status;
 203         struct pardev_cb        lm70llp_cb;
 204
 205         if (lm70llp) {
 206                 pr_warn("spi_lm70llp instance already loaded. Aborting.\n");
 207                 return;
 208         }
 209
 210         /* TODO:  this just _assumes_ a lm70 is there ... no probe;
 211          * the lm70 driver could verify it, reading the manf ID.
 212          */
 213
 214         master = spi_alloc_master(p->physport->dev, sizeof *pp);
 215         if (!master) {
 216                 status = -ENOMEM;
 217                 goto out_fail;
 218         }
 219         pp = spi_master_get_devdata(master);
 220
 221         /*
 222          * SPI and bitbang hookup.
 223          */
 224         pp->bitbang.master = master;
 225         pp->bitbang.chipselect = lm70_chipselect;
 226         pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 227         pp->bitbang.flags = SPI_3WIRE;
 228
 229         /*
 230          * Parport hookup
 231          */
 232         pp->port = p;
 233         memset(&lm70llp_cb, 0, sizeof(lm70llp_cb));
 234         lm70llp_cb.private = pp;
 235         lm70llp_cb.flags = PARPORT_FLAG_EXCL;
 236         pd = parport_register_dev_model(p, DRVNAME, &lm70llp_cb, 0);
 237
 238         if (!pd) {
 239                 status = -ENOMEM;
 240                 goto out_free_master;
 241         }
 242         pp->pd = pd;
 243
 244         status = parport_claim(pd);
 245         if (status < 0)
 246                 goto out_parport_unreg;
 247
 248         /*
 249          * Start SPI ...
 250          */
 251         status = spi_bitbang_start(&pp->bitbang);
 252         if (status < 0) {
 253                 dev_warn(&pd->dev, "spi_bitbang_start failed with status %d\n",
 254                          status);
 255                 goto out_off_and_release;
 256         }
 257
 258         /*
 259          * The modalias name MUST match the device_driver name
 260          * for the bus glue code to match and subsequently bind them.
 261          * We are binding to the generic drivers/hwmon/lm70.c device
 262          * driver.
 263          */
 264         strcpy(pp->info.modalias, "lm70");
 265         pp->info.max_speed_hz = 6 * 1000 * 1000;
 266         pp->info.chip_select = 0;
 267         pp->info.mode = SPI_3WIRE | SPI_MODE_0;
 268
 269         /* power up the chip, and let the LM70 control SI/SO */
 270         parport_write_data(pp->port, lm70_INIT);
 271
 272         /* Enable access to our primary data structure via
 273          * the board info's (void *)controller_data.
 274          */
 275         pp->info.controller_data = pp;
 276         pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
 277         if (pp->spidev_lm70)
 278                 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
 279                         dev_name(&pp->spidev_lm70->dev));
 280         else {
 281                 dev_warn(&pd->dev, "spi_new_device failed\n");
 282                 status = -ENODEV;
 283                 goto out_bitbang_stop;
 284         }
 285         pp->spidev_lm70->bits_per_word = 8;
 286
 287         lm70llp = pp;
 288         return;
 289
 290 out_bitbang_stop:
 291         spi_bitbang_stop(&pp->bitbang);
 292 out_off_and_release:
 293         /* power down */
 294         parport_write_data(pp->port, 0);
 295         mdelay(10);
 296         parport_release(pp->pd);
 297 out_parport_unreg:
 298         parport_unregister_device(pd);
 299 out_free_master:
 300         spi_master_put(master);
 301 out_fail:
 302         pr_info("spi_lm70llp probe fail, status %d\n", status);
 303 }
 304
 305 static void spi_lm70llp_detach(struct parport *p)
 306 {
 307         struct spi_lm70llp              *pp;
 308
 309         if (!lm70llp || lm70llp->port != p)
 310                 return;
 311
 312         pp = lm70llp;
 313         spi_bitbang_stop(&pp->bitbang);
 314
 315         /* power down */
 316         parport_write_data(pp->port, 0);
 317
 318         parport_release(pp->pd);
 319         parport_unregister_device(pp->pd);
 320
 321         spi_master_put(pp->bitbang.master);
 322
 323         lm70llp = NULL;
 324 }
 325
 326 static struct parport_driver spi_lm70llp_drv = {
 327         .name =         DRVNAME,
 328         .match_port =   spi_lm70llp_attach,
 329         .detach =       spi_lm70llp_detach,
 330         .devmodel =     true,
 331 };
 332
 333 static int __init init_spi_lm70llp(void)
 334 {
 335         return parport_register_driver(&spi_lm70llp_drv);
 336 }
 337 module_init(init_spi_lm70llp);
 338
 339 static void __exit cleanup_spi_lm70llp(void)
 340 {
 341         parport_unregister_driver(&spi_lm70llp_drv);
 342 }
 343 module_exit(cleanup_spi_lm70llp);
 344
 345 MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
 346 MODULE_DESCRIPTION(
 347         "Parport adapter for the National Semiconductor LM70 LLP eval board");
 348 MODULE_LICENSE("GPL");