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 /*
  25  * NOTE: this is an *EEPROM* driver.  The vagaries of product naming
  26  * mean that some AT25 products are EEPROMs, and others are FLASH.
  27  * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver,
  28  * not this one!
  29  */
  30
  31 struct at25_data {
  32         struct spi_device       *spi;
  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
  53 #define EE_MAXADDRLEN   3               /* 24 bit addresses, up to 2 MBytes */
  54
  55 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
  56  * it's important to recover from write timeouts.
  57  */
  58 #define EE_TIMEOUT      25
  59
  60 /*-------------------------------------------------------------------------*/
  61
  62 #define io_limit        PAGE_SIZE       /* bytes */
  63
  64 static ssize_t
  65 at25_ee_read(
  66         struct at25_data        *at25,
  67         char                    *buf,
  68         unsigned                offset,
  69         size_t                  count
  70 )
  71 {
  72         u8                      command[EE_MAXADDRLEN + 1];
  73         u8                      *cp;
  74         ssize_t                 status;
  75         struct spi_transfer     t[2];
  76         struct spi_message      m;
  77
  78         cp = command;
  79         *cp++ = AT25_READ;
  80
  81         /* 8/16/24-bit address is written MSB first */
  82         switch (at25->addrlen) {
  83         default:        /* case 3 */
  84                 *cp++ = offset >> 16;
  85         case 2:
  86                 *cp++ = offset >> 8;
  87         case 1:
  88         case 0: /* can't happen: for better codegen */
  89                 *cp++ = offset >> 0;
  90         }
  91
  92         spi_message_init(&m);
  93         memset(t, 0, sizeof t);
  94
  95         t[0].tx_buf = command;
  96         t[0].len = at25->addrlen + 1;
  97         spi_message_add_tail(&t[0], &m);
  98
  99         t[1].rx_buf = buf;
 100         t[1].len = count;
 101         spi_message_add_tail(&t[1], &m);
 102
 103         mutex_lock(&at25->lock);
 104
 105         /* Read it all at once.
 106          *
 107          * REVISIT that's potentially a problem with large chips, if
 108          * other devices on the bus need to be accessed regularly or
 109          * this chip is clocked very slowly
 110          */
 111         status = spi_sync(at25->spi, &m);
 112         dev_dbg(&at25->spi->dev,
 113                 "read %Zd bytes at %d --> %d\n",
 114                 count, offset, (int) status);
 115
 116         mutex_unlock(&at25->lock);
 117         return status ? status : count;
 118 }
 119
 120 static ssize_t
 121 at25_bin_read(struct kobject *kobj, struct bin_attribute *bin_attr,
 122               char *buf, loff_t off, size_t count)
 123 {
 124         struct device           *dev;
 125         struct at25_data        *at25;
 126
 127         dev = container_of(kobj, struct device, kobj);
 128         at25 = dev_get_drvdata(dev);
 129
 130         if (unlikely(off >= at25->bin.size))
 131                 return 0;
 132         if ((off + count) > at25->bin.size)
 133                 count = at25->bin.size - off;
 134         if (unlikely(!count))
 135                 return count;
 136
 137         return at25_ee_read(at25, buf, off, count);
 138 }
 139
 140
 141 static ssize_t
 142 at25_ee_write(struct at25_data *at25, char *buf, loff_t off, size_t count)
 143 {
 144         ssize_t                 status = 0;
 145         unsigned                written = 0;
 146         unsigned                buf_size;
 147         u8                      *bounce;
 148
 149         /* Temp buffer starts with command and address */
 150         buf_size = at25->chip.page_size;
 151         if (buf_size > io_limit)
 152                 buf_size = io_limit;
 153         bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
 154         if (!bounce)
 155                 return -ENOMEM;
 156
 157         /* For write, rollover is within the page ... so we write at
 158          * most one page, then manually roll over to the next page.
 159          */
 160         bounce[0] = AT25_WRITE;
 161         mutex_lock(&at25->lock);
 162         do {
 163                 unsigned long   timeout, retries;
 164                 unsigned        segment;
 165                 unsigned        offset = (unsigned) off;
 166                 u8              *cp = bounce + 1;
 167
 168                 *cp = AT25_WREN;
 169                 status = spi_write(at25->spi, cp, 1);
 170                 if (status < 0) {
 171                         dev_dbg(&at25->spi->dev, "WREN --> %d\n",
 172                                         (int) status);
 173                         break;
 174                 }
 175
 176                 /* 8/16/24-bit address is written MSB first */
 177                 switch (at25->addrlen) {
 178                 default:        /* case 3 */
 179                         *cp++ = offset >> 16;
 180                 case 2:
 181                         *cp++ = offset >> 8;
 182                 case 1:
 183                 case 0: /* can't happen: for better codegen */
 184                         *cp++ = offset >> 0;
 185                 }
 186
 187                 /* Write as much of a page as we can */
 188                 segment = buf_size - (offset % buf_size);
 189                 if (segment > count)
 190                         segment = count;
 191                 memcpy(cp, buf, segment);
 192                 status = spi_write(at25->spi, bounce,
 193                                 segment + at25->addrlen + 1);
 194                 dev_dbg(&at25->spi->dev,
 195                                 "write %u bytes at %u --> %d\n",
 196                                 segment, offset, (int) status);
 197                 if (status < 0)
 198                         break;
 199
 200                 /* REVISIT this should detect (or prevent) failed writes
 201                  * to readonly sections of the EEPROM...
 202                  */
 203
 204                 /* Wait for non-busy status */
 205                 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
 206                 retries = 0;
 207                 do {
 208                         int     sr;
 209
 210                         sr = spi_w8r8(at25->spi, AT25_RDSR);
 211                         if (sr < 0 || (sr & AT25_SR_nRDY)) {
 212                                 dev_dbg(&at25->spi->dev,
 213                                         "rdsr --> %d (%02x)\n", sr, sr);
 214                                 /* at HZ=100, this is sloooow */
 215                                 msleep(1);
 216                                 continue;
 217                         }
 218                         if (!(sr & AT25_SR_nRDY))
 219                                 break;
 220                 } while (retries++ < 3 || time_before_eq(jiffies, timeout));
 221
 222                 if (time_after(jiffies, timeout)) {
 223                         dev_err(&at25->spi->dev,
 224                                 "write %d bytes offset %d, "
 225                                 "timeout after %u msecs\n",
 226                                 segment, offset,
 227                                 jiffies_to_msecs(jiffies -
 228                                         (timeout - EE_TIMEOUT)));
 229                         status = -ETIMEDOUT;
 230                         break;
 231                 }
 232
 233                 off += segment;
 234                 buf += segment;
 235                 count -= segment;
 236                 written += segment;
 237
 238         } while (count > 0);
 239
 240         mutex_unlock(&at25->lock);
 241
 242         kfree(bounce);
 243         return written ? written : status;
 244 }
 245
 246 static ssize_t
 247 at25_bin_write(struct kobject *kobj, struct bin_attribute *bin_attr,
 248                char *buf, loff_t off, size_t count)
 249 {
 250         struct device           *dev;
 251         struct at25_data        *at25;
 252
 253         dev = container_of(kobj, struct device, kobj);
 254         at25 = dev_get_drvdata(dev);
 255
 256         if (unlikely(off >= at25->bin.size))
 257                 return -EFBIG;
 258         if ((off + count) > at25->bin.size)
 259                 count = at25->bin.size - off;
 260         if (unlikely(!count))
 261                 return count;
 262
 263         return at25_ee_write(at25, buf, off, count);
 264 }
 265
 266 /*-------------------------------------------------------------------------*/
 267
 268 static int at25_probe(struct spi_device *spi)
 269 {
 270         struct at25_data        *at25 = NULL;
 271         const struct spi_eeprom *chip;
 272         int                     err;
 273         int                     sr;
 274         int                     addrlen;
 275
 276         /* Chip description */
 277         chip = spi->dev.platform_data;
 278         if (!chip) {
 279                 dev_dbg(&spi->dev, "no chip description\n");
 280                 err = -ENODEV;
 281                 goto fail;
 282         }
 283
 284         /* For now we only support 8/16/24 bit addressing */
 285         if (chip->flags & EE_ADDR1)
 286                 addrlen = 1;
 287         else if (chip->flags & EE_ADDR2)
 288                 addrlen = 2;
 289         else if (chip->flags & EE_ADDR3)
 290                 addrlen = 3;
 291         else {
 292                 dev_dbg(&spi->dev, "unsupported address type\n");
 293                 err = -EINVAL;
 294                 goto fail;
 295         }
 296
 297         /* Ping the chip ... the status register is pretty portable,
 298          * unlike probing manufacturer IDs.  We do expect that system
 299          * firmware didn't write it in the past few milliseconds!
 300          */
 301         sr = spi_w8r8(spi, AT25_RDSR);
 302         if (sr < 0 || sr & AT25_SR_nRDY) {
 303                 dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
 304                 err = -ENXIO;
 305                 goto fail;
 306         }
 307
 308         if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
 309                 err = -ENOMEM;
 310                 goto fail;
 311         }
 312
 313         mutex_init(&at25->lock);
 314         at25->chip = *chip;
 315         at25->spi = spi_dev_get(spi);
 316         dev_set_drvdata(&spi->dev, at25);
 317         at25->addrlen = addrlen;
 318
 319         /* Export the EEPROM bytes through sysfs, since that's convenient.
 320          * Default to root-only access to the data; EEPROMs often hold data
 321          * that's sensitive for read and/or write, like ethernet addresses,
 322          * security codes, board-specific manufacturing calibrations, etc.
 323          */
 324         at25->bin.attr.name = "eeprom";
 325         at25->bin.attr.mode = S_IRUSR;
 326         at25->bin.read = at25_bin_read;
 327
 328         at25->bin.size = at25->chip.byte_len;
 329         if (!(chip->flags & EE_READONLY)) {
 330                 at25->bin.write = at25_bin_write;
 331                 at25->bin.attr.mode |= S_IWUSR;
 332         }
 333
 334         err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
 335         if (err)
 336                 goto fail;
 337
 338         dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
 339                 (at25->bin.size < 1024)
 340                         ? at25->bin.size
 341                         : (at25->bin.size / 1024),
 342                 (at25->bin.size < 1024) ? "Byte" : "KByte",
 343                 at25->chip.name,
 344                 (chip->flags & EE_READONLY) ? " (readonly)" : "",
 345                 at25->chip.page_size);
 346         return 0;
 347 fail:
 348         dev_dbg(&spi->dev, "probe err %d\n", err);
 349         kfree(at25);
 350         return err;
 351 }
 352
 353 static int __devexit at25_remove(struct spi_device *spi)
 354 {
 355         struct at25_data        *at25;
 356
 357         at25 = dev_get_drvdata(&spi->dev);
 358         sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
 359         kfree(at25);
 360         return 0;
 361 }
 362
 363 /*-------------------------------------------------------------------------*/
 364
 365 static struct spi_driver at25_driver = {
 366         .driver = {
 367                 .name           = "at25",
 368                 .owner          = THIS_MODULE,
 369         },
 370         .probe          = at25_probe,
 371         .remove         = __devexit_p(at25_remove),
 372 };
 373
 374 static int __init at25_init(void)
 375 {
 376         return spi_register_driver(&at25_driver);
 377 }
 378 module_init(at25_init);
 379
 380 static void __exit at25_exit(void)
 381 {
 382         spi_unregister_driver(&at25_driver);
 383 }
 384 module_exit(at25_exit);
 385
 386 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
 387 MODULE_AUTHOR("David Brownell");
 388 MODULE_LICENSE("GPL");
 389