linux/drivers/spi/spi-lm70llp.c
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   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 * 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
  83struct 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 */
  93static struct spi_lm70llp *lm70llp;
  94
  95
  96/*-------------------------------------------------------------------*/
  97
  98static 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
 110static 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
 118static 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
 126static 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
 132static 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
 140static inline void spidelay(unsigned d)
 141{
 142        udelay(d);
 143}
 144
 145static 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
 155static 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 */
 170static 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
 179static 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 */
 192static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
 193{
 194        return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits);
 195}
 196
 197static 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        /*
 223         * SPI and bitbang hookup.
 224         */
 225        pp->bitbang.master = spi_master_get(master);
 226        pp->bitbang.chipselect = lm70_chipselect;
 227        pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 228        pp->bitbang.flags = SPI_3WIRE;
 229
 230        /*
 231         * Parport hookup
 232         */
 233        pp->port = p;
 234        pd = parport_register_device(p, DRVNAME,
 235                        NULL, NULL, NULL,
 236                        PARPORT_FLAG_EXCL, pp);
 237        if (!pd) {
 238                status = -ENOMEM;
 239                goto out_free_master;
 240        }
 241        pp->pd = pd;
 242
 243        status = parport_claim(pd);
 244        if (status < 0)
 245                goto out_parport_unreg;
 246
 247        /*
 248         * Start SPI ...
 249         */
 250        status = spi_bitbang_start(&pp->bitbang);
 251        if (status < 0) {
 252                printk(KERN_WARNING
 253                        "%s: spi_bitbang_start failed with status %d\n",
 254                        DRVNAME, 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                printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
 282                status = -ENODEV;
 283                goto out_bitbang_stop;
 284        }
 285        pp->spidev_lm70->bits_per_word = 8;
 286
 287        lm70llp = pp;
 288        return;
 289
 290out_bitbang_stop:
 291        spi_bitbang_stop(&pp->bitbang);
 292out_off_and_release:
 293        /* power down */
 294        parport_write_data(pp->port, 0);
 295        mdelay(10);
 296        parport_release(pp->pd);
 297out_parport_unreg:
 298        parport_unregister_device(pd);
 299out_free_master:
 300        (void) spi_master_put(master);
 301out_fail:
 302        pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
 303}
 304
 305static 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        (void) spi_master_put(pp->bitbang.master);
 322
 323        lm70llp = NULL;
 324}
 325
 326
 327static struct parport_driver spi_lm70llp_drv = {
 328        .name =         DRVNAME,
 329        .attach =       spi_lm70llp_attach,
 330        .detach =       spi_lm70llp_detach,
 331};
 332
 333static int __init init_spi_lm70llp(void)
 334{
 335        return parport_register_driver(&spi_lm70llp_drv);
 336}
 337module_init(init_spi_lm70llp);
 338
 339static void __exit cleanup_spi_lm70llp(void)
 340{
 341        parport_unregister_driver(&spi_lm70llp_drv);
 342}
 343module_exit(cleanup_spi_lm70llp);
 344
 345MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
 346MODULE_DESCRIPTION(
 347        "Parport adapter for the National Semiconductor LM70 LLP eval board");
 348MODULE_LICENSE("GPL");
 349
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