drivers/spi/spi_lm70llp.c

   1 /*
   2  * spi_lm70llp.c - 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  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include <linux/init.h>
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/delay.h>
  25 #include <linux/device.h>
  26 #include <linux/parport.h>
  27 #include <linux/sysfs.h>
  28 #include <linux/workqueue.h>
  29
  30
  31 #include <linux/spi/spi.h>
  32 #include <linux/spi/spi_bitbang.h>
  33
  34
  35 /*
  36  * The LM70 communicates with a host processor using a 3-wire variant of
  37  * the SPI/Microwire bus interface. This driver specifically supports an
  38  * NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
  39  * port to bitbang an SPI-parport bridge.  Accordingly, this is an SPI
  40  * master controller driver.  The hwmon/lm70 driver is a "SPI protocol
  41  * driver", layered on top of this one and usable without the lm70llp.
  42  *
  43  * Datasheet and Schematic:
  44  * The LM70 is a temperature sensor chip from National Semiconductor; its
  45  * datasheet is available at http://www.national.com/pf/LM/LM70.html
  46  * The schematic for this particular board (the LM70EVAL-LLP) is
  47  * available (on page 4) here:
  48  *  http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
  49  *
  50  * Also see Documentation/spi/spi-lm70llp.  The SPI<->parport code here is
  51  * (heavily) based on spi-butterfly by David Brownell.
  52  *
  53  * The LM70 LLP connects to the PC parallel port in the following manner:
  54  *
  55  *   Parallel                 LM70 LLP
  56  *     Port      Direction   JP2 Header
  57  *  -----------  ---------  ------------
  58  *      D0    2      -         -
  59  *      D1    3     -->      V+   5
  60  *      D2    4     -->      V+   5
  61  *      D3    5     -->      V+   5
  62  *      D4    6     -->      V+   5
  63  *      D5    7     -->      nCS  8
  64  *      D6    8     -->      SCLK 3
  65  *      D7    9     -->      SI/O 5
  66  *     GND   25      -       GND  7
  67  *    Select 13     <--      SI/O 1
  68  *
  69  * Note that parport pin 13 actually gets inverted by the transistor
  70  * arrangement which lets either the parport or the LM70 drive the
  71  * SI/SO signal (see the schematic for details).
  72  */
  73
  74 #define DRVNAME         "spi-lm70llp"
  75
  76 #define lm70_INIT       0xBE
  77 #define SIO             0x10
  78 #define nCS             0x20
  79 #define SCLK            0x40
  80
  81 /*-------------------------------------------------------------------------*/
  82
  83 struct spi_lm70llp {
  84         struct spi_bitbang      bitbang;
  85         struct parport          *port;
  86         struct pardevice        *pd;
  87         struct spi_device       *spidev_lm70;
  88         struct spi_board_info   info;
  89         //struct device         *dev;
  90 };
  91
  92 /* REVISIT : ugly global ; provides "exclusive open" facility */
  93 static struct spi_lm70llp *lm70llp;
  94
  95
  96 /*-------------------------------------------------------------------*/
  97
  98 static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
  99 {
 100         return spi->controller_data;
 101 }
 102
 103 /*---------------------- LM70 LLP eval board-specific inlines follow */
 104
 105 /* NOTE:  we don't actually need to reread the output values, since they'll
 106  * still be what we wrote before.  Plus, going through parport builds in
 107  * a ~1ms/operation delay; these SPI transfers could easily be faster.
 108  */
 109
 110 static inline void deassertCS(struct spi_lm70llp *pp)
 111 {
 112         u8 data = parport_read_data(pp->port);
 113
 114         data &= ~0x80;          /* pull D7/SI-out low while de-asserted */
 115         parport_write_data(pp->port, data | nCS);
 116 }
 117
 118 static inline void assertCS(struct spi_lm70llp *pp)
 119 {
 120         u8 data = parport_read_data(pp->port);
 121
 122         data |= 0x80;           /* pull D7/SI-out high so lm70 drives SO-in */
 123         parport_write_data(pp->port, data & ~nCS);
 124 }
 125
 126 static inline void clkHigh(struct spi_lm70llp *pp)
 127 {
 128         u8 data = parport_read_data(pp->port);
 129         parport_write_data(pp->port, data | SCLK);
 130 }
 131
 132 static inline void clkLow(struct spi_lm70llp *pp)
 133 {
 134         u8 data = parport_read_data(pp->port);
 135         parport_write_data(pp->port, data & ~SCLK);
 136 }
 137
 138 /*------------------------- SPI-LM70-specific inlines ----------------------*/
 139
 140 static inline void spidelay(unsigned d)
 141 {
 142         udelay(d);
 143 }
 144
 145 static inline void setsck(struct spi_device *s, int is_on)
 146 {
 147         struct spi_lm70llp *pp = spidev_to_pp(s);
 148
 149         if (is_on)
 150                 clkHigh(pp);
 151         else
 152                 clkLow(pp);
 153 }
 154
 155 static inline void setmosi(struct spi_device *s, int is_on)
 156 {
 157         /* FIXME update D7 ... this way we can put the chip
 158          * into shutdown mode and read the manufacturer ID,
 159          * but we can't put it back into operational mode.
 160          */
 161 }
 162
 163 /*
 164  * getmiso:
 165  * Why do we return 0 when the SIO line is high and vice-versa?
 166  * The fact is, the lm70 eval board from NS (which this driver drives),
 167  * is wired in just such a way : when the lm70's SIO goes high, a transistor
 168  * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 169  */
 170 static inline int getmiso(struct spi_device *s)
 171 {
 172         struct spi_lm70llp *pp = spidev_to_pp(s);
 173         return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
 174 }
 175 /*--------------------------------------------------------------------*/
 176
 177 #include "spi_bitbang_txrx.h"
 178
 179 static void lm70_chipselect(struct spi_device *spi, int value)
 180 {
 181         struct spi_lm70llp *pp = spidev_to_pp(spi);
 182
 183         if (value)
 184                 assertCS(pp);
 185         else
 186                 deassertCS(pp);
 187 }
 188
 189 /*
 190  * Our actual bitbanger routine.
 191  */
 192 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
 193 {
 194         return bitbang_txrx_be_cpha0(spi, nsecs, 0, 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
 204         if (lm70llp) {
 205                 printk(KERN_WARNING
 206                         "%s: spi_lm70llp instance already loaded. Aborting.\n",
 207                         DRVNAME);
 208                 return;
 209         }
 210
 211         /* TODO:  this just _assumes_ a lm70 is there ... no probe;
 212          * the lm70 driver could verify it, reading the manf ID.
 213          */
 214
 215         master = spi_alloc_master(p->physport->dev, sizeof *pp);
 216         if (!master) {
 217                 status = -ENOMEM;
 218                 goto out_fail;
 219         }
 220         pp = spi_master_get_devdata(master);
 221
 222         master->bus_num = -1;   /* dynamic alloc of a bus number */
 223         master->num_chipselect = 1;
 224
 225         /*
 226          * SPI and bitbang hookup.
 227          */
 228         pp->bitbang.master = spi_master_get(master);
 229         pp->bitbang.chipselect = lm70_chipselect;
 230         pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 231         pp->bitbang.flags = SPI_3WIRE;
 232
 233         /*
 234          * Parport hookup
 235          */
 236         pp->port = p;
 237         pd = parport_register_device(p, DRVNAME,
 238                         NULL, NULL, NULL,
 239                         PARPORT_FLAG_EXCL, pp);
 240         if (!pd) {
 241                 status = -ENOMEM;
 242                 goto out_free_master;
 243         }
 244         pp->pd = pd;
 245
 246         status = parport_claim(pd);
 247         if (status < 0)
 248                 goto out_parport_unreg;
 249
 250         /*
 251          * Start SPI ...
 252          */
 253         status = spi_bitbang_start(&pp->bitbang);
 254         if (status < 0) {
 255                 printk(KERN_WARNING
 256                         "%s: spi_bitbang_start failed with status %d\n",
 257                         DRVNAME, status);
 258                 goto out_off_and_release;
 259         }
 260
 261         /*
 262          * The modalias name MUST match the device_driver name
 263          * for the bus glue code to match and subsequently bind them.
 264          * We are binding to the generic drivers/hwmon/lm70.c device
 265          * driver.
 266          */
 267         strcpy(pp->info.modalias, "lm70");
 268         pp->info.max_speed_hz = 6 * 1000 * 1000;
 269         pp->info.chip_select = 0;
 270         pp->info.mode = SPI_3WIRE | SPI_MODE_0;
 271
 272         /* power up the chip, and let the LM70 control SI/SO */
 273         parport_write_data(pp->port, lm70_INIT);
 274
 275         /* Enable access to our primary data structure via
 276          * the board info's (void *)controller_data.
 277          */
 278         pp->info.controller_data = pp;
 279         pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
 280         if (pp->spidev_lm70)
 281                 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
 282                                 dev_name(&pp->spidev_lm70->dev));
 283         else {
 284                 printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
 285                 status = -ENODEV;
 286                 goto out_bitbang_stop;
 287         }
 288         pp->spidev_lm70->bits_per_word = 8;
 289
 290         lm70llp = pp;
 291         return;
 292
 293 out_bitbang_stop:
 294         spi_bitbang_stop(&pp->bitbang);
 295 out_off_and_release:
 296         /* power down */
 297         parport_write_data(pp->port, 0);
 298         mdelay(10);
 299         parport_release(pp->pd);
 300 out_parport_unreg:
 301         parport_unregister_device(pd);
 302 out_free_master:
 303         (void) spi_master_put(master);
 304 out_fail:
 305         pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
 306 }
 307
 308 static void spi_lm70llp_detach(struct parport *p)
 309 {
 310         struct spi_lm70llp              *pp;
 311
 312         if (!lm70llp || lm70llp->port != p)
 313                 return;
 314
 315         pp = lm70llp;
 316         spi_bitbang_stop(&pp->bitbang);
 317
 318         /* power down */
 319         parport_write_data(pp->port, 0);
 320
 321         parport_release(pp->pd);
 322         parport_unregister_device(pp->pd);
 323
 324         (void) spi_master_put(pp->bitbang.master);
 325
 326         lm70llp = NULL;
 327 }
 328
 329
 330 static struct parport_driver spi_lm70llp_drv = {
 331         .name =         DRVNAME,
 332         .attach =       spi_lm70llp_attach,
 333         .detach =       spi_lm70llp_detach,
 334 };
 335
 336 static int __init init_spi_lm70llp(void)
 337 {
 338         return parport_register_driver(&spi_lm70llp_drv);
 339 }
 340 module_init(init_spi_lm70llp);
 341
 342 static void __exit cleanup_spi_lm70llp(void)
 343 {
 344         parport_unregister_driver(&spi_lm70llp_drv);
 345 }
 346 module_exit(cleanup_spi_lm70llp);
 347
 348 MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
 349 MODULE_DESCRIPTION(
 350         "Parport adapter for the National Semiconductor LM70 LLP eval board");
 351 MODULE_LICENSE("GPL");