drivers/misc/eeprom/at24.c

   1 /*
   2  * at24.c - handle most I2C EEPROMs
   3  *
   4  * Copyright (C) 2005-2007 David Brownell
   5  * Copyright (C) 2008 Wolfram Sang, Pengutronix
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  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/mutex.h>
  18 #include <linux/sysfs.h>
  19 #include <linux/mod_devicetable.h>
  20 #include <linux/log2.h>
  21 #include <linux/bitops.h>
  22 #include <linux/jiffies.h>
  23 #include <linux/i2c.h>
  24 #include <linux/i2c/at24.h>
  25
  26 /*
  27  * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
  28  * Differences between different vendor product lines (like Atmel AT24C or
  29  * MicroChip 24LC, etc) won't much matter for typical read/write access.
  30  * There are also I2C RAM chips, likewise interchangeable. One example
  31  * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
  32  *
  33  * However, misconfiguration can lose data. "Set 16-bit memory address"
  34  * to a part with 8-bit addressing will overwrite data. Writing with too
  35  * big a page size also loses data. And it's not safe to assume that the
  36  * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
  37  * uses 0x51, for just one example.
  38  *
  39  * Accordingly, explicit board-specific configuration data should be used
  40  * in almost all cases. (One partial exception is an SMBus used to access
  41  * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
  42  *
  43  * So this driver uses "new style" I2C driver binding, expecting to be
  44  * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
  45  * similar kernel-resident tables; or, configuration data coming from
  46  * a bootloader.
  47  *
  48  * Other than binding model, current differences from "eeprom" driver are
  49  * that this one handles write access and isn't restricted to 24c02 devices.
  50  * It also handles larger devices (32 kbit and up) with two-byte addresses,
  51  * which won't work on pure SMBus systems.
  52  */
  53
  54 struct at24_data {
  55         struct at24_platform_data chip;
  56         struct memory_accessor macc;
  57         bool use_smbus;
  58
  59         /*
  60          * Lock protects against activities from other Linux tasks,
  61          * but not from changes by other I2C masters.
  62          */
  63         struct mutex lock;
  64         struct bin_attribute bin;
  65
  66         u8 *writebuf;
  67         unsigned write_max;
  68         unsigned num_addresses;
  69
  70         /*
  71          * Some chips tie up multiple I2C addresses; dummy devices reserve
  72          * them for us, and we'll use them with SMBus calls.
  73          */
  74         struct i2c_client *client[];
  75 };
  76
  77 /*
  78  * This parameter is to help this driver avoid blocking other drivers out
  79  * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
  80  * clock, one 256 byte read takes about 1/43 second which is excessive;
  81  * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
  82  * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
  83  *
  84  * This value is forced to be a power of two so that writes align on pages.
  85  */
  86 static unsigned io_limit = 128;
  87 module_param(io_limit, uint, 0);
  88 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
  89
  90 /*
  91  * Specs often allow 5 msec for a page write, sometimes 20 msec;
  92  * it's important to recover from write timeouts.
  93  */
  94 static unsigned write_timeout = 25;
  95 module_param(write_timeout, uint, 0);
  96 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
  97
  98 #define AT24_SIZE_BYTELEN 5
  99 #define AT24_SIZE_FLAGS 8
 100
 101 #define AT24_BITMASK(x) (BIT(x) - 1)
 102
 103 /* create non-zero magic value for given eeprom parameters */
 104 #define AT24_DEVICE_MAGIC(_len, _flags)                 \
 105         ((1 << AT24_SIZE_FLAGS | (_flags))              \
 106             << AT24_SIZE_BYTELEN | ilog2(_len))
 107
 108 static const struct i2c_device_id at24_ids[] = {
 109         /* needs 8 addresses as A0-A2 are ignored */
 110         { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
 111         /* old variants can't be handled with this generic entry! */
 112         { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
 113         { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
 114         /* spd is a 24c02 in memory DIMMs */
 115         { "spd", AT24_DEVICE_MAGIC(2048 / 8,
 116                 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
 117         { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
 118         /* 24rf08 quirk is handled at i2c-core */
 119         { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
 120         { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
 121         { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
 122         { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
 123         { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
 124         { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
 125         { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
 126         { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
 127         { "at24", 0 },
 128         { /* END OF LIST */ }
 129 };
 130 MODULE_DEVICE_TABLE(i2c, at24_ids);
 131
 132 /*-------------------------------------------------------------------------*/
 133
 134 /*
 135  * This routine supports chips which consume multiple I2C addresses. It
 136  * computes the addressing information to be used for a given r/w request.
 137  * Assumes that sanity checks for offset happened at sysfs-layer.
 138  */
 139 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 140                 unsigned *offset)
 141 {
 142         unsigned i;
 143
 144         if (at24->chip.flags & AT24_FLAG_ADDR16) {
 145                 i = *offset >> 16;
 146                 *offset &= 0xffff;
 147         } else {
 148                 i = *offset >> 8;
 149                 *offset &= 0xff;
 150         }
 151
 152         return at24->client[i];
 153 }
 154
 155 static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
 156                 unsigned offset, size_t count)
 157 {
 158         struct i2c_msg msg[2];
 159         u8 msgbuf[2];
 160         struct i2c_client *client;
 161         unsigned long timeout, read_time;
 162         int status, i;
 163
 164         memset(msg, 0, sizeof(msg));
 165
 166         /*
 167          * REVISIT some multi-address chips don't rollover page reads to
 168          * the next slave address, so we may need to truncate the count.
 169          * Those chips might need another quirk flag.
 170          *
 171          * If the real hardware used four adjacent 24c02 chips and that
 172          * were misconfigured as one 24c08, that would be a similar effect:
 173          * one "eeprom" file not four, but larger reads would fail when
 174          * they crossed certain pages.
 175          */
 176
 177         /*
 178          * Slave address and byte offset derive from the offset. Always
 179          * set the byte address; on a multi-master board, another master
 180          * may have changed the chip's "current" address pointer.
 181          */
 182         client = at24_translate_offset(at24, &offset);
 183
 184         if (count > io_limit)
 185                 count = io_limit;
 186
 187         if (at24->use_smbus) {
 188                 /* Smaller eeproms can work given some SMBus extension calls */
 189                 if (count > I2C_SMBUS_BLOCK_MAX)
 190                         count = I2C_SMBUS_BLOCK_MAX;
 191         } else {
 192                 /*
 193                  * When we have a better choice than SMBus calls, use a
 194                  * combined I2C message. Write address; then read up to
 195                  * io_limit data bytes. Note that read page rollover helps us
 196                  * here (unlike writes). msgbuf is u8 and will cast to our
 197                  * needs.
 198                  */
 199                 i = 0;
 200                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 201                         msgbuf[i++] = offset >> 8;
 202                 msgbuf[i++] = offset;
 203
 204                 msg[0].addr = client->addr;
 205                 msg[0].buf = msgbuf;
 206                 msg[0].len = i;
 207
 208                 msg[1].addr = client->addr;
 209                 msg[1].flags = I2C_M_RD;
 210                 msg[1].buf = buf;
 211                 msg[1].len = count;
 212         }
 213
 214         /*
 215          * Reads fail if the previous write didn't complete yet. We may
 216          * loop a few times until this one succeeds, waiting at least
 217          * long enough for one entire page write to work.
 218          */
 219         timeout = jiffies + msecs_to_jiffies(write_timeout);
 220         do {
 221                 read_time = jiffies;
 222                 if (at24->use_smbus) {
 223                         status = i2c_smbus_read_i2c_block_data(client, offset,
 224                                         count, buf);
 225                 } else {
 226                         status = i2c_transfer(client->adapter, msg, 2);
 227                         if (status == 2)
 228                                 status = count;
 229                 }
 230                 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
 231                                 count, offset, status, jiffies);
 232
 233                 if (status == count)
 234                         return count;
 235
 236                 /* REVISIT: at HZ=100, this is sloooow */
 237                 msleep(1);
 238         } while (time_before(read_time, timeout));
 239
 240         return -ETIMEDOUT;
 241 }
 242
 243 static ssize_t at24_read(struct at24_data *at24,
 244                 char *buf, loff_t off, size_t count)
 245 {
 246         ssize_t retval = 0;
 247
 248         if (unlikely(!count))
 249                 return count;
 250
 251         /*
 252          * Read data from chip, protecting against concurrent updates
 253          * from this host, but not from other I2C masters.
 254          */
 255         mutex_lock(&at24->lock);
 256
 257         while (count) {
 258                 ssize_t status;
 259
 260                 status = at24_eeprom_read(at24, buf, off, count);
 261                 if (status <= 0) {
 262                         if (retval == 0)
 263                                 retval = status;
 264                         break;
 265                 }
 266                 buf += status;
 267                 off += status;
 268                 count -= status;
 269                 retval += status;
 270         }
 271
 272         mutex_unlock(&at24->lock);
 273
 274         return retval;
 275 }
 276
 277 static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
 278                 char *buf, loff_t off, size_t count)
 279 {
 280         struct at24_data *at24;
 281
 282         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 283         return at24_read(at24, buf, off, count);
 284 }
 285
 286
 287 /*
 288  * Note that if the hardware write-protect pin is pulled high, the whole
 289  * chip is normally write protected. But there are plenty of product
 290  * variants here, including OTP fuses and partial chip protect.
 291  *
 292  * We only use page mode writes; the alternative is sloooow. This routine
 293  * writes at most one page.
 294  */
 295 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 296                 unsigned offset, size_t count)
 297 {
 298         struct i2c_client *client;
 299         struct i2c_msg msg;
 300         ssize_t status;
 301         unsigned long timeout, write_time;
 302         unsigned next_page;
 303
 304         /* Get corresponding I2C address and adjust offset */
 305         client = at24_translate_offset(at24, &offset);
 306
 307         /* write_max is at most a page */
 308         if (count > at24->write_max)
 309                 count = at24->write_max;
 310
 311         /* Never roll over backwards, to the start of this page */
 312         next_page = roundup(offset + 1, at24->chip.page_size);
 313         if (offset + count > next_page)
 314                 count = next_page - offset;
 315
 316         /* If we'll use I2C calls for I/O, set up the message */
 317         if (!at24->use_smbus) {
 318                 int i = 0;
 319
 320                 msg.addr = client->addr;
 321                 msg.flags = 0;
 322
 323                 /* msg.buf is u8 and casts will mask the values */
 324                 msg.buf = at24->writebuf;
 325                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 326                         msg.buf[i++] = offset >> 8;
 327
 328                 msg.buf[i++] = offset;
 329                 memcpy(&msg.buf[i], buf, count);
 330                 msg.len = i + count;
 331         }
 332
 333         /*
 334          * Writes fail if the previous one didn't complete yet. We may
 335          * loop a few times until this one succeeds, waiting at least
 336          * long enough for one entire page write to work.
 337          */
 338         timeout = jiffies + msecs_to_jiffies(write_timeout);
 339         do {
 340                 write_time = jiffies;
 341                 if (at24->use_smbus) {
 342                         status = i2c_smbus_write_i2c_block_data(client,
 343                                         offset, count, buf);
 344                         if (status == 0)
 345                                 status = count;
 346                 } else {
 347                         status = i2c_transfer(client->adapter, &msg, 1);
 348                         if (status == 1)
 349                                 status = count;
 350                 }
 351                 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
 352                                 count, offset, status, jiffies);
 353
 354                 if (status == count)
 355                         return count;
 356
 357                 /* REVISIT: at HZ=100, this is sloooow */
 358                 msleep(1);
 359         } while (time_before(write_time, timeout));
 360
 361         return -ETIMEDOUT;
 362 }
 363
 364 static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 365                           size_t count)
 366 {
 367         ssize_t retval = 0;
 368
 369         if (unlikely(!count))
 370                 return count;
 371
 372         /*
 373          * Write data to chip, protecting against concurrent updates
 374          * from this host, but not from other I2C masters.
 375          */
 376         mutex_lock(&at24->lock);
 377
 378         while (count) {
 379                 ssize_t status;
 380
 381                 status = at24_eeprom_write(at24, buf, off, count);
 382                 if (status <= 0) {
 383                         if (retval == 0)
 384                                 retval = status;
 385                         break;
 386                 }
 387                 buf += status;
 388                 off += status;
 389                 count -= status;
 390                 retval += status;
 391         }
 392
 393         mutex_unlock(&at24->lock);
 394
 395         return retval;
 396 }
 397
 398 static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
 399                 char *buf, loff_t off, size_t count)
 400 {
 401         struct at24_data *at24;
 402
 403         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 404         return at24_write(at24, buf, off, count);
 405 }
 406
 407 /*-------------------------------------------------------------------------*/
 408
 409 /*
 410  * This lets other kernel code access the eeprom data. For example, it
 411  * might hold a board's Ethernet address, or board-specific calibration
 412  * data generated on the manufacturing floor.
 413  */
 414
 415 static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
 416                          off_t offset, size_t count)
 417 {
 418         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 419
 420         return at24_read(at24, buf, offset, count);
 421 }
 422
 423 static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
 424                           off_t offset, size_t count)
 425 {
 426         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 427
 428         return at24_write(at24, buf, offset, count);
 429 }
 430
 431 /*-------------------------------------------------------------------------*/
 432
 433 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 434 {
 435         struct at24_platform_data chip;
 436         bool writable;
 437         bool use_smbus = false;
 438         struct at24_data *at24;
 439         int err;
 440         unsigned i, num_addresses;
 441         kernel_ulong_t magic;
 442
 443         if (client->dev.platform_data) {
 444                 chip = *(struct at24_platform_data *)client->dev.platform_data;
 445         } else {
 446                 if (!id->driver_data) {
 447                         err = -ENODEV;
 448                         goto err_out;
 449                 }
 450                 magic = id->driver_data;
 451                 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
 452                 magic >>= AT24_SIZE_BYTELEN;
 453                 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
 454                 /*
 455                  * This is slow, but we can't know all eeproms, so we better
 456                  * play safe. Specifying custom eeprom-types via platform_data
 457                  * is recommended anyhow.
 458                  */
 459                 chip.page_size = 1;
 460
 461                 chip.setup = NULL;
 462                 chip.context = NULL;
 463         }
 464
 465         if (!is_power_of_2(chip.byte_len))
 466                 dev_warn(&client->dev,
 467                         "byte_len looks suspicious (no power of 2)!\n");
 468         if (!is_power_of_2(chip.page_size))
 469                 dev_warn(&client->dev,
 470                         "page_size looks suspicious (no power of 2)!\n");
 471
 472         /* Use I2C operations unless we're stuck with SMBus extensions. */
 473         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 474                 if (chip.flags & AT24_FLAG_ADDR16) {
 475                         err = -EPFNOSUPPORT;
 476                         goto err_out;
 477                 }
 478                 if (!i2c_check_functionality(client->adapter,
 479                                 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 480                         err = -EPFNOSUPPORT;
 481                         goto err_out;
 482                 }
 483                 use_smbus = true;
 484         }
 485
 486         if (chip.flags & AT24_FLAG_TAKE8ADDR)
 487                 num_addresses = 8;
 488         else
 489                 num_addresses = DIV_ROUND_UP(chip.byte_len,
 490                         (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
 491
 492         at24 = kzalloc(sizeof(struct at24_data) +
 493                 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
 494         if (!at24) {
 495                 err = -ENOMEM;
 496                 goto err_out;
 497         }
 498
 499         mutex_init(&at24->lock);
 500         at24->use_smbus = use_smbus;
 501         at24->chip = chip;
 502         at24->num_addresses = num_addresses;
 503
 504         /*
 505          * Export the EEPROM bytes through sysfs, since that's convenient.
 506          * By default, only root should see the data (maybe passwords etc)
 507          */
 508         sysfs_bin_attr_init(&at24->bin);
 509         at24->bin.attr.name = "eeprom";
 510         at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
 511         at24->bin.read = at24_bin_read;
 512         at24->bin.size = chip.byte_len;
 513
 514         at24->macc.read = at24_macc_read;
 515
 516         writable = !(chip.flags & AT24_FLAG_READONLY);
 517         if (writable) {
 518                 if (!use_smbus || i2c_check_functionality(client->adapter,
 519                                 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 520
 521                         unsigned write_max = chip.page_size;
 522
 523                         at24->macc.write = at24_macc_write;
 524
 525                         at24->bin.write = at24_bin_write;
 526                         at24->bin.attr.mode |= S_IWUSR;
 527
 528                         if (write_max > io_limit)
 529                                 write_max = io_limit;
 530                         if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
 531                                 write_max = I2C_SMBUS_BLOCK_MAX;
 532                         at24->write_max = write_max;
 533
 534                         /* buffer (data + address at the beginning) */
 535                         at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL);
 536                         if (!at24->writebuf) {
 537                                 err = -ENOMEM;
 538                                 goto err_struct;
 539                         }
 540                 } else {
 541                         dev_warn(&client->dev,
 542                                 "cannot write due to controller restrictions.");
 543                 }
 544         }
 545
 546         at24->client[0] = client;
 547
 548         /* use dummy devices for multiple-address chips */
 549         for (i = 1; i < num_addresses; i++) {
 550                 at24->client[i] = i2c_new_dummy(client->adapter,
 551                                         client->addr + i);
 552                 if (!at24->client[i]) {
 553                         dev_err(&client->dev, "address 0x%02x unavailable\n",
 554                                         client->addr + i);
 555                         err = -EADDRINUSE;
 556                         goto err_clients;
 557                 }
 558         }
 559
 560         err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
 561         if (err)
 562                 goto err_clients;
 563
 564         i2c_set_clientdata(client, at24);
 565
 566         dev_info(&client->dev, "%zu byte %s EEPROM %s\n",
 567                 at24->bin.size, client->name,
 568                 writable ? "(writable)" : "(read-only)");
 569         dev_dbg(&client->dev,
 570                 "page_size %d, num_addresses %d, write_max %d%s\n",
 571                 chip.page_size, num_addresses,
 572                 at24->write_max,
 573                 use_smbus ? ", use_smbus" : "");
 574
 575         /* export data to kernel code */
 576         if (chip.setup)
 577                 chip.setup(&at24->macc, chip.context);
 578
 579         return 0;
 580
 581 err_clients:
 582         for (i = 1; i < num_addresses; i++)
 583                 if (at24->client[i])
 584                         i2c_unregister_device(at24->client[i]);
 585
 586         kfree(at24->writebuf);
 587 err_struct:
 588         kfree(at24);
 589 err_out:
 590         dev_dbg(&client->dev, "probe error %d\n", err);
 591         return err;
 592 }
 593
 594 static int __devexit at24_remove(struct i2c_client *client)
 595 {
 596         struct at24_data *at24;
 597         int i;
 598
 599         at24 = i2c_get_clientdata(client);
 600         sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
 601
 602         for (i = 1; i < at24->num_addresses; i++)
 603                 i2c_unregister_device(at24->client[i]);
 604
 605         kfree(at24->writebuf);
 606         kfree(at24);
 607         i2c_set_clientdata(client, NULL);
 608         return 0;
 609 }
 610
 611 /*-------------------------------------------------------------------------*/
 612
 613 static struct i2c_driver at24_driver = {
 614         .driver = {
 615                 .name = "at24",
 616                 .owner = THIS_MODULE,
 617         },
 618         .probe = at24_probe,
 619         .remove = __devexit_p(at24_remove),
 620         .id_table = at24_ids,
 621 };
 622
 623 static int __init at24_init(void)
 624 {
 625         io_limit = rounddown_pow_of_two(io_limit);
 626         return i2c_add_driver(&at24_driver);
 627 }
 628 module_init(at24_init);
 629
 630 static void __exit at24_exit(void)
 631 {
 632         i2c_del_driver(&at24_driver);
 633 }
 634 module_exit(at24_exit);
 635
 636 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
 637 MODULE_AUTHOR("David Brownell and Wolfram Sang");
 638 MODULE_LICENSE("GPL");