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