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 #define EXPAND_BITBANG_TXRX 1
 178 #include <linux/spi/spi_bitbang.h>
 179
 180 static void lm70_chipselect(struct spi_device *spi, int value)
 181 {
 182         struct spi_lm70llp *pp = spidev_to_pp(spi);
 183
 184         if (value)
 185                 assertCS(pp);
 186         else
 187                 deassertCS(pp);
 188 }
 189
 190 /*
 191  * Our actual bitbanger routine.
 192  */
 193 static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
 194 {
 195         return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
 196 }
 197
 198 static void spi_lm70llp_attach(struct parport *p)
 199 {
 200         struct pardevice        *pd;
 201         struct spi_lm70llp      *pp;
 202         struct spi_master       *master;
 203         int                     status;
 204
 205         if (lm70llp) {
 206                 printk(KERN_WARNING
 207                         "%s: spi_lm70llp instance already loaded. Aborting.\n",
 208                         DRVNAME);
 209                 return;
 210         }
 211
 212         /* TODO:  this just _assumes_ a lm70 is there ... no probe;
 213          * the lm70 driver could verify it, reading the manf ID.
 214          */
 215
 216         master = spi_alloc_master(p->physport->dev, sizeof *pp);
 217         if (!master) {
 218                 status = -ENOMEM;
 219                 goto out_fail;
 220         }
 221         pp = spi_master_get_devdata(master);
 222
 223         master->bus_num = -1;   /* dynamic alloc of a bus number */
 224         master->num_chipselect = 1;
 225
 226         /*
 227          * SPI and bitbang hookup.
 228          */
 229         pp->bitbang.master = spi_master_get(master);
 230         pp->bitbang.chipselect = lm70_chipselect;
 231         pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
 232         pp->bitbang.flags = SPI_3WIRE;
 233
 234         /*
 235          * Parport hookup
 236          */
 237         pp->port = p;
 238         pd = parport_register_device(p, DRVNAME,
 239                         NULL, NULL, NULL,
 240                         PARPORT_FLAG_EXCL, pp);
 241         if (!pd) {
 242                 status = -ENOMEM;
 243                 goto out_free_master;
 244         }
 245         pp->pd = pd;
 246
 247         status = parport_claim(pd);
 248         if (status < 0)
 249                 goto out_parport_unreg;
 250
 251         /*
 252          * Start SPI ...
 253          */
 254         status = spi_bitbang_start(&pp->bitbang);
 255         if (status < 0) {
 256                 printk(KERN_WARNING
 257                         "%s: spi_bitbang_start failed with status %d\n",
 258                         DRVNAME, status);
 259                 goto out_off_and_release;
 260         }
 261
 262         /*
 263          * The modalias name MUST match the device_driver name
 264          * for the bus glue code to match and subsequently bind them.
 265          * We are binding to the generic drivers/hwmon/lm70.c device
 266          * driver.
 267          */
 268         strcpy(pp->info.modalias, "lm70");
 269         pp->info.max_speed_hz = 6 * 1000 * 1000;
 270         pp->info.chip_select = 0;
 271         pp->info.mode = SPI_3WIRE | SPI_MODE_0;
 272
 273         /* power up the chip, and let the LM70 control SI/SO */
 274         parport_write_data(pp->port, lm70_INIT);
 275
 276         /* Enable access to our primary data structure via
 277          * the board info's (void *)controller_data.
 278          */
 279         pp->info.controller_data = pp;
 280         pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
 281         if (pp->spidev_lm70)
 282                 dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
 283                                 dev_name(&pp->spidev_lm70->dev));
 284         else {
 285                 printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
 286                 status = -ENODEV;
 287                 goto out_bitbang_stop;
 288         }
 289         pp->spidev_lm70->bits_per_word = 8;
 290
 291         lm70llp = pp;
 292         return;
 293
 294 out_bitbang_stop:
 295         spi_bitbang_stop(&pp->bitbang);
 296 out_off_and_release:
 297         /* power down */
 298         parport_write_data(pp->port, 0);
 299         mdelay(10);
 300         parport_release(pp->pd);
 301 out_parport_unreg:
 302         parport_unregister_device(pd);
 303 out_free_master:
 304         (void) spi_master_put(master);
 305 out_fail:
 306         pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
 307 }
 308
 309 static void spi_lm70llp_detach(struct parport *p)
 310 {
 311         struct spi_lm70llp              *pp;
 312
 313         if (!lm70llp || lm70llp->port != p)
 314                 return;
 315
 316         pp = lm70llp;
 317         spi_bitbang_stop(&pp->bitbang);
 318
 319         /* power down */
 320         parport_write_data(pp->port, 0);
 321
 322         parport_release(pp->pd);
 323         parport_unregister_device(pp->pd);
 324
 325         (void) spi_master_put(pp->bitbang.master);
 326
 327         lm70llp = NULL;
 328 }
 329
 330
 331 static struct parport_driver spi_lm70llp_drv = {
 332         .name =         DRVNAME,
 333         .attach =       spi_lm70llp_attach,
 334         .detach =       spi_lm70llp_detach,
 335 };
 336
 337 static int __init init_spi_lm70llp(void)
 338 {
 339         return parport_register_driver(&spi_lm70llp_drv);
 340 }
 341 module_init(init_spi_lm70llp);
 342
 343 static void __exit cleanup_spi_lm70llp(void)
 344 {
 345         parport_unregister_driver(&spi_lm70llp_drv);
 346 }
 347 module_exit(cleanup_spi_lm70llp);
 348
 349 MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
 350 MODULE_DESCRIPTION(
 351         "Parport adapter for the National Semiconductor LM70 LLP eval board");
 352 MODULE_LICENSE("GPL");