drivers/spi/at25.c

   1 /*
   2  * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
   3  *
   4  * Copyright (C) 2006 David Brownell
   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
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/module.h>
  15 #include <linux/slab.h>
  16 #include <linux/delay.h>
  17 #include <linux/device.h>
  18 #include <linux/sched.h>
  19
  20 #include <linux/spi/spi.h>
  21 #include <linux/spi/eeprom.h>
  22
  23
  24 struct at25_data {
  25         struct spi_device       *spi;
  26         struct mutex            lock;
  27         struct spi_eeprom       chip;
  28         struct bin_attribute    bin;
  29         unsigned                addrlen;
  30 };
  31
  32 #define AT25_WREN       0x06            /* latch the write enable */
  33 #define AT25_WRDI       0x04            /* reset the write enable */
  34 #define AT25_RDSR       0x05            /* read status register */
  35 #define AT25_WRSR       0x01            /* write status register */
  36 #define AT25_READ       0x03            /* read byte(s) */
  37 #define AT25_WRITE      0x02            /* write byte(s)/sector */
  38
  39 #define AT25_SR_nRDY    0x01            /* nRDY = write-in-progress */
  40 #define AT25_SR_WEN     0x02            /* write enable (latched) */
  41 #define AT25_SR_BP0     0x04            /* BP for software writeprotect */
  42 #define AT25_SR_BP1     0x08
  43 #define AT25_SR_WPEN    0x80            /* writeprotect enable */
  44
  45
  46 #define EE_MAXADDRLEN   3               /* 24 bit addresses, up to 2 MBytes */
  47
  48 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
  49  * it's important to recover from write timeouts.
  50  */
  51 #define EE_TIMEOUT      25
  52
  53 /*-------------------------------------------------------------------------*/
  54
  55 #define io_limit        PAGE_SIZE       /* bytes */
  56
  57 static ssize_t
  58 at25_ee_read(
  59         struct at25_data        *at25,
  60         char                    *buf,
  61         unsigned                offset,
  62         size_t                  count
  63 )
  64 {
  65         u8                      command[EE_MAXADDRLEN + 1];
  66         u8                      *cp;
  67         ssize_t                 status;
  68         struct spi_transfer     t[2];
  69         struct spi_message      m;
  70
  71         cp = command;
  72         *cp++ = AT25_READ;
  73
  74         /* 8/16/24-bit address is written MSB first */
  75         switch (at25->addrlen) {
  76         default:        /* case 3 */
  77                 *cp++ = offset >> 16;
  78         case 2:
  79                 *cp++ = offset >> 8;
  80         case 1:
  81         case 0: /* can't happen: for better codegen */
  82                 *cp++ = offset >> 0;
  83         }
  84
  85         spi_message_init(&m);
  86         memset(t, 0, sizeof t);
  87
  88         t[0].tx_buf = command;
  89         t[0].len = at25->addrlen + 1;
  90         spi_message_add_tail(&t[0], &m);
  91
  92         t[1].rx_buf = buf;
  93         t[1].len = count;
  94         spi_message_add_tail(&t[1], &m);
  95
  96         mutex_lock(&at25->lock);
  97
  98         /* Read it all at once.
  99          *
 100          * REVISIT that's potentially a problem with large chips, if
 101          * other devices on the bus need to be accessed regularly or
 102          * this chip is clocked very slowly
 103          */
 104         status = spi_sync(at25->spi, &m);
 105         dev_dbg(&at25->spi->dev,
 106                 "read %Zd bytes at %d --> %d\n",
 107                 count, offset, (int) status);
 108
 109         mutex_unlock(&at25->lock);
 110         return status ? status : count;
 111 }
 112
 113 static ssize_t
 114 at25_bin_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
 115 {
 116         struct device           *dev;
 117         struct at25_data        *at25;
 118
 119         dev = container_of(kobj, struct device, kobj);
 120         at25 = dev_get_drvdata(dev);
 121
 122         if (unlikely(off >= at25->bin.size))
 123                 return 0;
 124         if ((off + count) > at25->bin.size)
 125                 count = at25->bin.size - off;
 126         if (unlikely(!count))
 127                 return count;
 128
 129         return at25_ee_read(at25, buf, off, count);
 130 }
 131
 132
 133 static ssize_t
 134 at25_ee_write(struct at25_data *at25, char *buf, loff_t off, size_t count)
 135 {
 136         ssize_t                 status = 0;
 137         unsigned                written = 0;
 138         unsigned                buf_size;
 139         u8                      *bounce;
 140
 141         /* Temp buffer starts with command and address */
 142         buf_size = at25->chip.page_size;
 143         if (buf_size > io_limit)
 144                 buf_size = io_limit;
 145         bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
 146         if (!bounce)
 147                 return -ENOMEM;
 148
 149         /* For write, rollover is within the page ... so we write at
 150          * most one page, then manually roll over to the next page.
 151          */
 152         bounce[0] = AT25_WRITE;
 153         mutex_lock(&at25->lock);
 154         do {
 155                 unsigned long   timeout, retries;
 156                 unsigned        segment;
 157                 unsigned        offset = (unsigned) off;
 158                 u8              *cp = bounce + 1;
 159
 160                 *cp = AT25_WREN;
 161                 status = spi_write(at25->spi, cp, 1);
 162                 if (status < 0) {
 163                         dev_dbg(&at25->spi->dev, "WREN --> %d\n",
 164                                         (int) status);
 165                         break;
 166                 }
 167
 168                 /* 8/16/24-bit address is written MSB first */
 169                 switch (at25->addrlen) {
 170                 default:        /* case 3 */
 171                         *cp++ = offset >> 16;
 172                 case 2:
 173                         *cp++ = offset >> 8;
 174                 case 1:
 175                 case 0: /* can't happen: for better codegen */
 176                         *cp++ = offset >> 0;
 177                 }
 178
 179                 /* Write as much of a page as we can */
 180                 segment = buf_size - (offset % buf_size);
 181                 if (segment > count)
 182                         segment = count;
 183                 memcpy(cp, buf, segment);
 184                 status = spi_write(at25->spi, bounce,
 185                                 segment + at25->addrlen + 1);
 186                 dev_dbg(&at25->spi->dev,
 187                                 "write %u bytes at %u --> %d\n",
 188                                 segment, offset, (int) status);
 189                 if (status < 0)
 190                         break;
 191
 192                 /* REVISIT this should detect (or prevent) failed writes
 193                  * to readonly sections of the EEPROM...
 194                  */
 195
 196                 /* Wait for non-busy status */
 197                 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
 198                 retries = 0;
 199                 do {
 200                         int     sr;
 201
 202                         sr = spi_w8r8(at25->spi, AT25_RDSR);
 203                         if (sr < 0 || (sr & AT25_SR_nRDY)) {
 204                                 dev_dbg(&at25->spi->dev,
 205                                         "rdsr --> %d (%02x)\n", sr, sr);
 206                                 /* at HZ=100, this is sloooow */
 207                                 msleep(1);
 208                                 continue;
 209                         }
 210                         if (!(sr & AT25_SR_nRDY))
 211                                 break;
 212                 } while (retries++ < 3 || time_before_eq(jiffies, timeout));
 213
 214                 if (time_after(jiffies, timeout)) {
 215                         dev_err(&at25->spi->dev,
 216                                 "write %d bytes offset %d, "
 217                                 "timeout after %u msecs\n",
 218                                 segment, offset,
 219                                 jiffies_to_msecs(jiffies -
 220                                         (timeout - EE_TIMEOUT)));
 221                         status = -ETIMEDOUT;
 222                         break;
 223                 }
 224
 225                 off += segment;
 226                 buf += segment;
 227                 count -= segment;
 228                 written += segment;
 229
 230         } while (count > 0);
 231
 232         mutex_unlock(&at25->lock);
 233
 234         kfree(bounce);
 235         return written ? written : status;
 236 }
 237
 238 static ssize_t
 239 at25_bin_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
 240 {
 241         struct device           *dev;
 242         struct at25_data        *at25;
 243
 244         dev = container_of(kobj, struct device, kobj);
 245         at25 = dev_get_drvdata(dev);
 246
 247         if (unlikely(off >= at25->bin.size))
 248                 return -EFBIG;
 249         if ((off + count) > at25->bin.size)
 250                 count = at25->bin.size - off;
 251         if (unlikely(!count))
 252                 return count;
 253
 254         return at25_ee_write(at25, buf, off, count);
 255 }
 256
 257 /*-------------------------------------------------------------------------*/
 258
 259 static int at25_probe(struct spi_device *spi)
 260 {
 261         struct at25_data        *at25 = NULL;
 262         const struct spi_eeprom *chip;
 263         int                     err;
 264         int                     sr;
 265         int                     addrlen;
 266
 267         /* Chip description */
 268         chip = spi->dev.platform_data;
 269         if (!chip) {
 270                 dev_dbg(&spi->dev, "no chip description\n");
 271                 err = -ENODEV;
 272                 goto fail;
 273         }
 274
 275         /* For now we only support 8/16/24 bit addressing */
 276         if (chip->flags & EE_ADDR1)
 277                 addrlen = 1;
 278         else if (chip->flags & EE_ADDR2)
 279                 addrlen = 2;
 280         else if (chip->flags & EE_ADDR3)
 281                 addrlen = 3;
 282         else {
 283                 dev_dbg(&spi->dev, "unsupported address type\n");
 284                 err = -EINVAL;
 285                 goto fail;
 286         }
 287
 288         /* Ping the chip ... the status register is pretty portable,
 289          * unlike probing manufacturer IDs.  We do expect that system
 290          * firmware didn't write it in the past few milliseconds!
 291          */
 292         sr = spi_w8r8(spi, AT25_RDSR);
 293         if (sr < 0 || sr & AT25_SR_nRDY) {
 294                 dev_dbg(&at25->spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
 295                 err = -ENXIO;
 296                 goto fail;
 297         }
 298
 299         if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
 300                 err = -ENOMEM;
 301                 goto fail;
 302         }
 303
 304         mutex_init(&at25->lock);
 305         at25->chip = *chip;
 306         at25->spi = spi_dev_get(spi);
 307         dev_set_drvdata(&spi->dev, at25);
 308         at25->addrlen = addrlen;
 309
 310         /* Export the EEPROM bytes through sysfs, since that's convenient.
 311          * Default to root-only access to the data; EEPROMs often hold data
 312          * that's sensitive for read and/or write, like ethernet addresses,
 313          * security codes, board-specific manufacturing calibrations, etc.
 314          */
 315         at25->bin.attr.name = "eeprom";
 316         at25->bin.attr.mode = S_IRUSR;
 317         at25->bin.attr.owner = THIS_MODULE;
 318         at25->bin.read = at25_bin_read;
 319
 320         at25->bin.size = at25->chip.byte_len;
 321         if (!(chip->flags & EE_READONLY)) {
 322                 at25->bin.write = at25_bin_write;
 323                 at25->bin.attr.mode |= S_IWUSR;
 324         }
 325
 326         err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
 327         if (err)
 328                 goto fail;
 329
 330         dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
 331                 (at25->bin.size < 1024)
 332                         ? at25->bin.size
 333                         : (at25->bin.size / 1024),
 334                 (at25->bin.size < 1024) ? "Byte" : "KByte",
 335                 at25->chip.name,
 336                 (chip->flags & EE_READONLY) ? " (readonly)" : "",
 337                 at25->chip.page_size);
 338         return 0;
 339 fail:
 340         dev_dbg(&spi->dev, "probe err %d\n", err);
 341         kfree(at25);
 342         return err;
 343 }
 344
 345 static int __devexit at25_remove(struct spi_device *spi)
 346 {
 347         struct at25_data        *at25;
 348
 349         at25 = dev_get_drvdata(&spi->dev);
 350         sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
 351         kfree(at25);
 352         return 0;
 353 }
 354
 355 /*-------------------------------------------------------------------------*/
 356
 357 static struct spi_driver at25_driver = {
 358         .driver = {
 359                 .name           = "at25",
 360                 .owner          = THIS_MODULE,
 361         },
 362         .probe          = at25_probe,
 363         .remove         = __devexit_p(at25_remove),
 364 };
 365
 366 static int __init at25_init(void)
 367 {
 368         return spi_register_driver(&at25_driver);
 369 }
 370 module_init(at25_init);
 371
 372 static void __exit at25_exit(void)
 373 {
 374         spi_unregister_driver(&at25_driver);
 375 }
 376 module_exit(at25_exit);
 377
 378 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
 379 MODULE_AUTHOR("David Brownell");
 380 MODULE_LICENSE("GPL");
 381