drivers/spi/spi_lm70llp.c

   1 /*
   2  * spi_lm70llp.c - driver for lm70llp eval 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  * The LM70 is a temperature sensor chip from National Semiconductor; its
  44  * datasheet is available at http://www.national.com/pf/LM/LM70.html
  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.
  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         parport_write_data(pp->port, data | nCS);
 110 }
 111
 112 static inline void assertCS(struct spi_lm70llp *pp)
 113 {
 114         u8 data = parport_read_data(pp->port);
 115         parport_write_data(pp->port, data & ~nCS);
 116 }
 117
 118 static inline void clkHigh(struct spi_lm70llp *pp)
 119 {
 120         u8 data = parport_read_data(pp->port);
 121         parport_write_data(pp->port, data | SCLK);
 122 }
 123
 124 static inline void clkLow(struct spi_lm70llp *pp)
 125 {
 126         u8 data = parport_read_data(pp->port);
 127         parport_write_data(pp->port, data & ~SCLK);
 128 }
 129
 130 /*------------------------- SPI-LM70-specific inlines ----------------------*/
 131
 132 static inline void spidelay(unsigned d)
 133 {
 134         udelay(d);
 135 }
 136
 137 static inline void setsck(struct spi_device *s, int is_on)
 138 {
 139         struct spi_lm70llp *pp = spidev_to_pp(s);
 140
 141         if (is_on)
 142                 clkHigh(pp);
 143         else
 144                 clkLow(pp);
 145 }
 146
 147 static inline void setmosi(struct spi_device *s, int is_on)
 148 {
 149         /* FIXME update D7 ... this way we can put the chip
 150          * into shutdown mode and read the manufacturer ID,
 151          * but we can't put it back into operational mode.
 152          */
 153 }
 154
 155 /*
 156  * getmiso:
 157  * Why do we return 0 when the SIO line is high and vice-versa?
 158  * The fact is, the lm70 eval board from NS (which this driver drives),
 159  * is wired in just such a way : when the lm70's SIO goes high, a transistor
 160  * switches it to low reflecting this on the parport (pin 13), and vice-versa.
 161  */
 162 static inline int getmiso(struct spi_device *s)
 163 {
 164         struct spi_lm70llp *pp = spidev_to_pp(s);
 165         return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
 166 }
 167 /*--------------------------------------------------------------------*/
 168
 169 #define EXPAND_BITBANG_TXRX 1
 170 #include <linux/spi/spi_bitbang.h>
 171
 172 static void lm70_chipselect(struct spi_device *spi, int value)
 173 {
 174         struct spi_lm70llp *pp = spidev_to_pp(spi);
 175
 176         if (value)
 177                 assertCS(pp);
 178         else
 179                 deassertCS(pp);
 180 }
 181
 182 /*
 183  * Our actual bitbanger routine.
 184  */
 185 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
 186 {
 187         static u32 sio=0;
 188         static int first_time=1;
 189
 190         /* First time: perform SPI bitbang and return the LSB of
 191          * the result of the SPI call.
 192          */
 193         if (first_time) {
 194                 sio = bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
 195                 first_time=0;
 196                 return (sio & 0x00ff);
 197         }
 198         /* Return the MSB of the result of the SPI call */
 199         else {
 200                 first_time=1;
 201                 return (sio >> 8);
 202         }
 203 }
 204
 205 static void spi_lm70llp_attach(struct parport *p)
 206 {
 207         struct pardevice        *pd;
 208         struct spi_lm70llp      *pp;
 209         struct spi_master       *master;
 210         int                     status;
 211
 212         if (lm70llp) {
 213                 printk(KERN_WARNING
 214                         "%s: spi_lm70llp instance already loaded. Aborting.\n",
 215                         DRVNAME);
 216                 return;
 217         }
 218
 219         /* TODO:  this just _assumes_ a lm70 is there ... no probe;
 220          * the lm70 driver could verify it, reading the manf ID.
 221          */
 222
 223         master = spi_alloc_master(p->physport->dev, sizeof *pp);
 224         if (!master) {
 225                 status = -ENOMEM;
 226                 goto out_fail;
 227         }
 228         pp = spi_master_get_devdata(master);
 229
 230         master->bus_num = -1;   /* dynamic alloc of a bus number */
 231         master->num_chipselect = 1;
 232
 233         /*
 234          * SPI and bitbang hookup.
 235          */
 236         pp->bitbang.master = spi_master_get(master);
 237         pp->bitbang.chipselect = lm70_chipselect;
 238         pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 239         pp->bitbang.flags = SPI_3WIRE;
 240
 241         /*
 242          * Parport hookup
 243          */
 244         pp->port = p;
 245         pd = parport_register_device(p, DRVNAME,
 246                         NULL, NULL, NULL,
 247                         PARPORT_FLAG_EXCL, pp);
 248         if (!pd) {
 249                 status = -ENOMEM;
 250                 goto out_free_master;
 251         }
 252         pp->pd = pd;
 253
 254         status = parport_claim(pd);
 255         if (status < 0)
 256                 goto out_parport_unreg;
 257
 258         /*
 259          * Start SPI ...
 260          */
 261         status = spi_bitbang_start(&pp->bitbang);
 262         if (status < 0) {
 263                 printk(KERN_WARNING
 264                         "%s: spi_bitbang_start failed with status %d\n",
 265                         DRVNAME, status);
 266                 goto out_off_and_release;
 267         }
 268
 269         /*
 270          * The modalias name MUST match the device_driver name
 271          * for the bus glue code to match and subsequently bind them.
 272          * We are binding to the generic drivers/hwmon/lm70.c device
 273          * driver.
 274          */
 275         strcpy(pp->info.modalias, "lm70");
 276         pp->info.max_speed_hz = 6 * 1000 * 1000;
 277         pp->info.chip_select = 0;
 278         pp->info.mode = SPI_3WIRE | SPI_MODE_0;
 279
 280         /* power up the chip, and let the LM70 control SI/SO */
 281         parport_write_data(pp->port, lm70_INIT);
 282
 283         /* Enable access to our primary data structure via
 284          * the board info's (void *)controller_data.
 285          */
 286         pp->info.controller_data = pp;
 287         pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
 288         if (pp->spidev_lm70)
 289                 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
 290                                 pp->spidev_lm70->dev.bus_id);
 291         else {
 292                 printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
 293                 status = -ENODEV;
 294                 goto out_bitbang_stop;
 295         }
 296         pp->spidev_lm70->bits_per_word = 16;
 297
 298         lm70llp = pp;
 299
 300         return;
 301
 302 out_bitbang_stop:
 303         spi_bitbang_stop(&pp->bitbang);
 304 out_off_and_release:
 305         /* power down */
 306         parport_write_data(pp->port, 0);
 307         mdelay(10);
 308         parport_release(pp->pd);
 309 out_parport_unreg:
 310         parport_unregister_device(pd);
 311 out_free_master:
 312         (void) spi_master_put(master);
 313 out_fail:
 314         pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
 315 }
 316
 317 static void spi_lm70llp_detach(struct parport *p)
 318 {
 319         struct spi_lm70llp              *pp;
 320
 321         if (!lm70llp || lm70llp->port != p)
 322                 return;
 323
 324         pp = lm70llp;
 325         spi_bitbang_stop(&pp->bitbang);
 326
 327         /* power down */
 328         parport_write_data(pp->port, 0);
 329         msleep(10);
 330
 331         parport_release(pp->pd);
 332         parport_unregister_device(pp->pd);
 333
 334         (void) spi_master_put(pp->bitbang.master);
 335
 336         lm70llp = NULL;
 337 }
 338
 339
 340 static struct parport_driver spi_lm70llp_drv = {
 341         .name =         DRVNAME,
 342         .attach =       spi_lm70llp_attach,
 343         .detach =       spi_lm70llp_detach,
 344 };
 345
 346 static int __init init_spi_lm70llp(void)
 347 {
 348         return parport_register_driver(&spi_lm70llp_drv);
 349 }
 350 module_init(init_spi_lm70llp);
 351
 352 static void __exit cleanup_spi_lm70llp(void)
 353 {
 354         parport_unregister_driver(&spi_lm70llp_drv);
 355 }
 356 module_exit(cleanup_spi_lm70llp);
 357
 358 MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
 359 MODULE_DESCRIPTION(
 360         "Parport adapter for the National Semiconductor LM70 LLP eval board");
 361 MODULE_LICENSE("GPL");