drivers/misc/eeprom/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/module.h>
  14 #include <linux/slab.h>
  15 #include <linux/delay.h>
  16 #include <linux/device.h>
  17 #include <linux/sched.h>
  18
  19 #include <linux/spi/spi.h>
  20 #include <linux/spi/eeprom.h>
  21 #include <linux/of.h>
  22
  23 /*
  24  * NOTE: this is an *EEPROM* driver.  The vagaries of product naming
  25  * mean that some AT25 products are EEPROMs, and others are FLASH.
  26  * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver,
  27  * not this one!
  28  */
  29
  30 struct at25_data {
  31         struct spi_device       *spi;
  32         struct memory_accessor  mem;
  33         struct mutex            lock;
  34         struct spi_eeprom       chip;
  35         struct bin_attribute    bin;
  36         unsigned                addrlen;
  37 };
  38
  39 #define AT25_WREN       0x06            /* latch the write enable */
  40 #define AT25_WRDI       0x04            /* reset the write enable */
  41 #define AT25_RDSR       0x05            /* read status register */
  42 #define AT25_WRSR       0x01            /* write status register */
  43 #define AT25_READ       0x03            /* read byte(s) */
  44 #define AT25_WRITE      0x02            /* write byte(s)/sector */
  45
  46 #define AT25_SR_nRDY    0x01            /* nRDY = write-in-progress */
  47 #define AT25_SR_WEN     0x02            /* write enable (latched) */
  48 #define AT25_SR_BP0     0x04            /* BP for software writeprotect */
  49 #define AT25_SR_BP1     0x08
  50 #define AT25_SR_WPEN    0x80            /* writeprotect enable */
  51
  52 #define AT25_INSTR_BIT3 0x08            /* Additional address bit in instr */
  53
  54 #define EE_MAXADDRLEN   3               /* 24 bit addresses, up to 2 MBytes */
  55
  56 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
  57  * it's important to recover from write timeouts.
  58  */
  59 #define EE_TIMEOUT      25
  60
  61 /*-------------------------------------------------------------------------*/
  62
  63 #define io_limit        PAGE_SIZE       /* bytes */
  64
  65 static ssize_t
  66 at25_ee_read(
  67         struct at25_data        *at25,
  68         char                    *buf,
  69         unsigned                offset,
  70         size_t                  count
  71 )
  72 {
  73         u8                      command[EE_MAXADDRLEN + 1];
  74         u8                      *cp;
  75         ssize_t                 status;
  76         struct spi_transfer     t[2];
  77         struct spi_message      m;
  78         u8                      instr;
  79
  80         if (unlikely(offset >= at25->bin.size))
  81                 return 0;
  82         if ((offset + count) > at25->bin.size)
  83                 count = at25->bin.size - offset;
  84         if (unlikely(!count))
  85                 return count;
  86
  87         cp = command;
  88
  89         instr = AT25_READ;
  90         if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
  91                 if (offset >= (1U << (at25->addrlen * 8)))
  92                         instr |= AT25_INSTR_BIT3;
  93         *cp++ = instr;
  94
  95         /* 8/16/24-bit address is written MSB first */
  96         switch (at25->addrlen) {
  97         default:        /* case 3 */
  98                 *cp++ = offset >> 16;
  99         case 2:
 100                 *cp++ = offset >> 8;
 101         case 1:
 102         case 0: /* can't happen: for better codegen */
 103                 *cp++ = offset >> 0;
 104         }
 105
 106         spi_message_init(&m);
 107         memset(t, 0, sizeof t);
 108
 109         t[0].tx_buf = command;
 110         t[0].len = at25->addrlen + 1;
 111         spi_message_add_tail(&t[0], &m);
 112
 113         t[1].rx_buf = buf;
 114         t[1].len = count;
 115         spi_message_add_tail(&t[1], &m);
 116
 117         mutex_lock(&at25->lock);
 118
 119         /* Read it all at once.
 120          *
 121          * REVISIT that's potentially a problem with large chips, if
 122          * other devices on the bus need to be accessed regularly or
 123          * this chip is clocked very slowly
 124          */
 125         status = spi_sync(at25->spi, &m);
 126         dev_dbg(&at25->spi->dev,
 127                 "read %Zd bytes at %d --> %d\n",
 128                 count, offset, (int) status);
 129
 130         mutex_unlock(&at25->lock);
 131         return status ? status : count;
 132 }
 133
 134 static ssize_t
 135 at25_bin_read(struct file *filp, struct kobject *kobj,
 136               struct bin_attribute *bin_attr,
 137               char *buf, loff_t off, size_t count)
 138 {
 139         struct device           *dev;
 140         struct at25_data        *at25;
 141
 142         dev = container_of(kobj, struct device, kobj);
 143         at25 = dev_get_drvdata(dev);
 144
 145         return at25_ee_read(at25, buf, off, count);
 146 }
 147
 148
 149 static ssize_t
 150 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off,
 151               size_t count)
 152 {
 153         ssize_t                 status = 0;
 154         unsigned                written = 0;
 155         unsigned                buf_size;
 156         u8                      *bounce;
 157
 158         if (unlikely(off >= at25->bin.size))
 159                 return -EFBIG;
 160         if ((off + count) > at25->bin.size)
 161                 count = at25->bin.size - off;
 162         if (unlikely(!count))
 163                 return count;
 164
 165         /* Temp buffer starts with command and address */
 166         buf_size = at25->chip.page_size;
 167         if (buf_size > io_limit)
 168                 buf_size = io_limit;
 169         bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
 170         if (!bounce)
 171                 return -ENOMEM;
 172
 173         /* For write, rollover is within the page ... so we write at
 174          * most one page, then manually roll over to the next page.
 175          */
 176         mutex_lock(&at25->lock);
 177         do {
 178                 unsigned long   timeout, retries;
 179                 unsigned        segment;
 180                 unsigned        offset = (unsigned) off;
 181                 u8              *cp = bounce;
 182                 int             sr;
 183                 u8              instr;
 184
 185                 *cp = AT25_WREN;
 186                 status = spi_write(at25->spi, cp, 1);
 187                 if (status < 0) {
 188                         dev_dbg(&at25->spi->dev, "WREN --> %d\n",
 189                                         (int) status);
 190                         break;
 191                 }
 192
 193                 instr = AT25_WRITE;
 194                 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
 195                         if (offset >= (1U << (at25->addrlen * 8)))
 196                                 instr |= AT25_INSTR_BIT3;
 197                 *cp++ = instr;
 198
 199                 /* 8/16/24-bit address is written MSB first */
 200                 switch (at25->addrlen) {
 201                 default:        /* case 3 */
 202                         *cp++ = offset >> 16;
 203                 case 2:
 204                         *cp++ = offset >> 8;
 205                 case 1:
 206                 case 0: /* can't happen: for better codegen */
 207                         *cp++ = offset >> 0;
 208                 }
 209
 210                 /* Write as much of a page as we can */
 211                 segment = buf_size - (offset % buf_size);
 212                 if (segment > count)
 213                         segment = count;
 214                 memcpy(cp, buf, segment);
 215                 status = spi_write(at25->spi, bounce,
 216                                 segment + at25->addrlen + 1);
 217                 dev_dbg(&at25->spi->dev,
 218                                 "write %u bytes at %u --> %d\n",
 219                                 segment, offset, (int) status);
 220                 if (status < 0)
 221                         break;
 222
 223                 /* REVISIT this should detect (or prevent) failed writes
 224                  * to readonly sections of the EEPROM...
 225                  */
 226
 227                 /* Wait for non-busy status */
 228                 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
 229                 retries = 0;
 230                 do {
 231
 232                         sr = spi_w8r8(at25->spi, AT25_RDSR);
 233                         if (sr < 0 || (sr & AT25_SR_nRDY)) {
 234                                 dev_dbg(&at25->spi->dev,
 235                                         "rdsr --> %d (%02x)\n", sr, sr);
 236                                 /* at HZ=100, this is sloooow */
 237                                 msleep(1);
 238                                 continue;
 239                         }
 240                         if (!(sr & AT25_SR_nRDY))
 241                                 break;
 242                 } while (retries++ < 3 || time_before_eq(jiffies, timeout));
 243
 244                 if ((sr < 0) || (sr & AT25_SR_nRDY)) {
 245                         dev_err(&at25->spi->dev,
 246                                 "write %d bytes offset %d, "
 247                                 "timeout after %u msecs\n",
 248                                 segment, offset,
 249                                 jiffies_to_msecs(jiffies -
 250                                         (timeout - EE_TIMEOUT)));
 251                         status = -ETIMEDOUT;
 252                         break;
 253                 }
 254
 255                 off += segment;
 256                 buf += segment;
 257                 count -= segment;
 258                 written += segment;
 259
 260         } while (count > 0);
 261
 262         mutex_unlock(&at25->lock);
 263
 264         kfree(bounce);
 265         return written ? written : status;
 266 }
 267
 268 static ssize_t
 269 at25_bin_write(struct file *filp, struct kobject *kobj,
 270                struct bin_attribute *bin_attr,
 271                char *buf, loff_t off, size_t count)
 272 {
 273         struct device           *dev;
 274         struct at25_data        *at25;
 275
 276         dev = container_of(kobj, struct device, kobj);
 277         at25 = dev_get_drvdata(dev);
 278
 279         return at25_ee_write(at25, buf, off, count);
 280 }
 281
 282 /*-------------------------------------------------------------------------*/
 283
 284 /* Let in-kernel code access the eeprom data. */
 285
 286 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf,
 287                          off_t offset, size_t count)
 288 {
 289         struct at25_data *at25 = container_of(mem, struct at25_data, mem);
 290
 291         return at25_ee_read(at25, buf, offset, count);
 292 }
 293
 294 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf,
 295                           off_t offset, size_t count)
 296 {
 297         struct at25_data *at25 = container_of(mem, struct at25_data, mem);
 298
 299         return at25_ee_write(at25, buf, offset, count);
 300 }
 301
 302 /*-------------------------------------------------------------------------*/
 303
 304 static int at25_np_to_chip(struct device *dev,
 305                            struct device_node *np,
 306                            struct spi_eeprom *chip)
 307 {
 308         u32 val;
 309
 310         memset(chip, 0, sizeof(*chip));
 311         strncpy(chip->name, np->name, sizeof(chip->name));
 312
 313         if (of_property_read_u32(np, "size", &val) == 0 ||
 314             of_property_read_u32(np, "at25,byte-len", &val) == 0) {
 315                 chip->byte_len = val;
 316         } else {
 317                 dev_err(dev, "Error: missing \"size\" property\n");
 318                 return -ENODEV;
 319         }
 320
 321         if (of_property_read_u32(np, "pagesize", &val) == 0 ||
 322             of_property_read_u32(np, "at25,page-size", &val) == 0) {
 323                 chip->page_size = (u16)val;
 324         } else {
 325                 dev_err(dev, "Error: missing \"pagesize\" property\n");
 326                 return -ENODEV;
 327         }
 328
 329         if (of_property_read_u32(np, "at25,addr-mode", &val) == 0) {
 330                 chip->flags = (u16)val;
 331         } else {
 332                 if (of_property_read_u32(np, "address-width", &val)) {
 333                         dev_err(dev,
 334                                 "Error: missing \"address-width\" property\n");
 335                         return -ENODEV;
 336                 }
 337                 switch (val) {
 338                 case 8:
 339                         chip->flags |= EE_ADDR1;
 340                         break;
 341                 case 16:
 342                         chip->flags |= EE_ADDR2;
 343                         break;
 344                 case 24:
 345                         chip->flags |= EE_ADDR3;
 346                         break;
 347                 default:
 348                         dev_err(dev,
 349                                 "Error: bad \"address-width\" property: %u\n",
 350                                 val);
 351                         return -ENODEV;
 352                 }
 353                 if (of_find_property(np, "read-only", NULL))
 354                         chip->flags |= EE_READONLY;
 355         }
 356         return 0;
 357 }
 358
 359 static int at25_probe(struct spi_device *spi)
 360 {
 361         struct at25_data        *at25 = NULL;
 362         struct spi_eeprom       chip;
 363         struct device_node      *np = spi->dev.of_node;
 364         int                     err;
 365         int                     sr;
 366         int                     addrlen;
 367
 368         /* Chip description */
 369         if (!spi->dev.platform_data) {
 370                 if (np) {
 371                         err = at25_np_to_chip(&spi->dev, np, &chip);
 372                         if (err)
 373                                 return err;
 374                 } else {
 375                         dev_err(&spi->dev, "Error: no chip description\n");
 376                         return -ENODEV;
 377                 }
 378         } else
 379                 chip = *(struct spi_eeprom *)spi->dev.platform_data;
 380
 381         /* For now we only support 8/16/24 bit addressing */
 382         if (chip.flags & EE_ADDR1)
 383                 addrlen = 1;
 384         else if (chip.flags & EE_ADDR2)
 385                 addrlen = 2;
 386         else if (chip.flags & EE_ADDR3)
 387                 addrlen = 3;
 388         else {
 389                 dev_dbg(&spi->dev, "unsupported address type\n");
 390                 return -EINVAL;
 391         }
 392
 393         /* Ping the chip ... the status register is pretty portable,
 394          * unlike probing manufacturer IDs.  We do expect that system
 395          * firmware didn't write it in the past few milliseconds!
 396          */
 397         sr = spi_w8r8(spi, AT25_RDSR);
 398         if (sr < 0 || sr & AT25_SR_nRDY) {
 399                 dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
 400                 return -ENXIO;
 401         }
 402
 403         at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL);
 404         if (!at25)
 405                 return -ENOMEM;
 406
 407         mutex_init(&at25->lock);
 408         at25->chip = chip;
 409         at25->spi = spi_dev_get(spi);
 410         spi_set_drvdata(spi, at25);
 411         at25->addrlen = addrlen;
 412
 413         /* Export the EEPROM bytes through sysfs, since that's convenient.
 414          * And maybe to other kernel code; it might hold a board's Ethernet
 415          * address, or board-specific calibration data generated on the
 416          * manufacturing floor.
 417          *
 418          * Default to root-only access to the data; EEPROMs often hold data
 419          * that's sensitive for read and/or write, like ethernet addresses,
 420          * security codes, board-specific manufacturing calibrations, etc.
 421          */
 422         sysfs_bin_attr_init(&at25->bin);
 423         at25->bin.attr.name = "eeprom";
 424         at25->bin.attr.mode = S_IRUSR;
 425         at25->bin.read = at25_bin_read;
 426         at25->mem.read = at25_mem_read;
 427
 428         at25->bin.size = at25->chip.byte_len;
 429         if (!(chip.flags & EE_READONLY)) {
 430                 at25->bin.write = at25_bin_write;
 431                 at25->bin.attr.mode |= S_IWUSR;
 432                 at25->mem.write = at25_mem_write;
 433         }
 434
 435         err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
 436         if (err)
 437                 return err;
 438
 439         if (chip.setup)
 440                 chip.setup(&at25->mem, chip.context);
 441
 442         dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
 443                 (at25->bin.size < 1024)
 444                         ? at25->bin.size
 445                         : (at25->bin.size / 1024),
 446                 (at25->bin.size < 1024) ? "Byte" : "KByte",
 447                 at25->chip.name,
 448                 (chip.flags & EE_READONLY) ? " (readonly)" : "",
 449                 at25->chip.page_size);
 450         return 0;
 451 }
 452
 453 static int at25_remove(struct spi_device *spi)
 454 {
 455         struct at25_data        *at25;
 456
 457         at25 = spi_get_drvdata(spi);
 458         sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
 459         return 0;
 460 }
 461
 462 /*-------------------------------------------------------------------------*/
 463
 464 static const struct of_device_id at25_of_match[] = {
 465         { .compatible = "atmel,at25", },
 466         { }
 467 };
 468 MODULE_DEVICE_TABLE(of, at25_of_match);
 469
 470 static struct spi_driver at25_driver = {
 471         .driver = {
 472                 .name           = "at25",
 473                 .owner          = THIS_MODULE,
 474                 .of_match_table = at25_of_match,
 475         },
 476         .probe          = at25_probe,
 477         .remove         = at25_remove,
 478 };
 479
 480 module_spi_driver(at25_driver);
 481
 482 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
 483 MODULE_AUTHOR("David Brownell");
 484 MODULE_LICENSE("GPL");
 485 MODULE_ALIAS("spi:at25");