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
  27 #include <linux/spi/spi.h>
  28 #include <linux/spi/spi_bitbang.h>
  29
  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
  94 static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
  95 {
  96         return spi->controller_data;
  97 }
  98
  99 /*---------------------- LM70 LLP eval board-specific inlines follow */
 100
 101 /* NOTE:  we don't actually need to reread the output values, since they'll
 102  * still be what we wrote before.  Plus, going through parport builds in
 103  * a ~1ms/operation delay; these SPI transfers could easily be faster.
 104  */
 105
 106 static inline void deassertCS(struct spi_lm70llp *pp)
 107 {
 108         u8 data = parport_read_data(pp->port);
 109
 110         data &= ~0x80;          /* pull D7/SI-out low while de-asserted */
 111         parport_write_data(pp->port, data | nCS);
 112 }
 113
 114 static inline void assertCS(struct spi_lm70llp *pp)
 115 {
 116         u8 data = parport_read_data(pp->port);
 117
 118         data |= 0x80;           /* pull D7/SI-out high so lm70 drives SO-in */
 119         parport_write_data(pp->port, data & ~nCS);
 120 }
 121
 122 static inline void clkHigh(struct spi_lm70llp *pp)
 123 {
 124         u8 data = parport_read_data(pp->port);
 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         parport_write_data(pp->port, data & ~SCLK);
 132 }
 133
 134 /*------------------------- SPI-LM70-specific inlines ----------------------*/
 135
 136 static inline void spidelay(unsigned d)
 137 {
 138         udelay(d);
 139 }
 140
 141 static inline void setsck(struct spi_device *s, int is_on)
 142 {
 143         struct spi_lm70llp *pp = spidev_to_pp(s);
 144
 145         if (is_on)
 146                 clkHigh(pp);
 147         else
 148                 clkLow(pp);
 149 }
 150
 151 static inline void setmosi(struct spi_device *s, int is_on)
 152 {
 153         /* FIXME update D7 ... this way we can put the chip
 154          * into shutdown mode and read the manufacturer ID,
 155          * but we can't put it back into operational mode.
 156          */
 157 }
 158
 159 /*
 160  * getmiso:
 161  * Why do we return 0 when the SIO line is high and vice-versa?
 162  * The fact is, the lm70 eval board from NS (which this driver drives),
 163  * is wired in just such a way : when the lm70's SIO goes high, a transistor
 164  * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 165  */
 166 static inline int getmiso(struct spi_device *s)
 167 {
 168         struct spi_lm70llp *pp = spidev_to_pp(s);
 169         return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
 170 }
 171 /*--------------------------------------------------------------------*/
 172
 173 #include "spi-bitbang-txrx.h"
 174
 175 static void lm70_chipselect(struct spi_device *spi, int value)
 176 {
 177         struct spi_lm70llp *pp = spidev_to_pp(spi);
 178
 179         if (value)
 180                 assertCS(pp);
 181         else
 182                 deassertCS(pp);
 183 }
 184
 185 /*
 186  * Our actual bitbanger routine.
 187  */
 188 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
 189 {
 190         return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
 191 }
 192
 193 static void spi_lm70llp_attach(struct parport *p)
 194 {
 195         struct pardevice        *pd;
 196         struct spi_lm70llp      *pp;
 197         struct spi_master       *master;
 198         int                     status;
 199
 200         if (lm70llp) {
 201                 printk(KERN_WARNING
 202                         "%s: spi_lm70llp instance already loaded. Aborting.\n",
 203                         DRVNAME);
 204                 return;
 205         }
 206
 207         /* TODO:  this just _assumes_ a lm70 is there ... no probe;
 208          * the lm70 driver could verify it, reading the manf ID.
 209          */
 210
 211         master = spi_alloc_master(p->physport->dev, sizeof *pp);
 212         if (!master) {
 213                 status = -ENOMEM;
 214                 goto out_fail;
 215         }
 216         pp = spi_master_get_devdata(master);
 217
 218         /*
 219          * SPI and bitbang hookup.
 220          */
 221         pp->bitbang.master = master;
 222         pp->bitbang.chipselect = lm70_chipselect;
 223         pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 224         pp->bitbang.flags = SPI_3WIRE;
 225
 226         /*
 227          * Parport hookup
 228          */
 229         pp->port = p;
 230         pd = parport_register_device(p, DRVNAME,
 231                         NULL, NULL, NULL,
 232                         PARPORT_FLAG_EXCL, pp);
 233         if (!pd) {
 234                 status = -ENOMEM;
 235                 goto out_free_master;
 236         }
 237         pp->pd = pd;
 238
 239         status = parport_claim(pd);
 240         if (status < 0)
 241                 goto out_parport_unreg;
 242
 243         /*
 244          * Start SPI ...
 245          */
 246         status = spi_bitbang_start(&pp->bitbang);
 247         if (status < 0) {
 248                 printk(KERN_WARNING
 249                         "%s: spi_bitbang_start failed with status %d\n",
 250                         DRVNAME, status);
 251                 goto out_off_and_release;
 252         }
 253
 254         /*
 255          * The modalias name MUST match the device_driver name
 256          * for the bus glue code to match and subsequently bind them.
 257          * We are binding to the generic drivers/hwmon/lm70.c device
 258          * driver.
 259          */
 260         strcpy(pp->info.modalias, "lm70");
 261         pp->info.max_speed_hz = 6 * 1000 * 1000;
 262         pp->info.chip_select = 0;
 263         pp->info.mode = SPI_3WIRE | SPI_MODE_0;
 264
 265         /* power up the chip, and let the LM70 control SI/SO */
 266         parport_write_data(pp->port, lm70_INIT);
 267
 268         /* Enable access to our primary data structure via
 269          * the board info's (void *)controller_data.
 270          */
 271         pp->info.controller_data = pp;
 272         pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
 273         if (pp->spidev_lm70)
 274                 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
 275                                 dev_name(&pp->spidev_lm70->dev));
 276         else {
 277                 printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
 278                 status = -ENODEV;
 279                 goto out_bitbang_stop;
 280         }
 281         pp->spidev_lm70->bits_per_word = 8;
 282
 283         lm70llp = pp;
 284         return;
 285
 286 out_bitbang_stop:
 287         spi_bitbang_stop(&pp->bitbang);
 288 out_off_and_release:
 289         /* power down */
 290         parport_write_data(pp->port, 0);
 291         mdelay(10);
 292         parport_release(pp->pd);
 293 out_parport_unreg:
 294         parport_unregister_device(pd);
 295 out_free_master:
 296         (void) spi_master_put(master);
 297 out_fail:
 298         pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
 299 }
 300
 301 static void spi_lm70llp_detach(struct parport *p)
 302 {
 303         struct spi_lm70llp              *pp;
 304
 305         if (!lm70llp || lm70llp->port != p)
 306                 return;
 307
 308         pp = lm70llp;
 309         spi_bitbang_stop(&pp->bitbang);
 310
 311         /* power down */
 312         parport_write_data(pp->port, 0);
 313
 314         parport_release(pp->pd);
 315         parport_unregister_device(pp->pd);
 316
 317         (void) spi_master_put(pp->bitbang.master);
 318
 319         lm70llp = NULL;
 320 }
 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");