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-rw-r--r--drivers/misc/eeprom/at24.c582
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diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
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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
54struct at24_data {
55 struct at24_platform_data chip;
56 bool use_smbus;
57
58 /*
59 * Lock protects against activities from other Linux tasks,
60 * but not from changes by other I2C masters.
61 */
62 struct mutex lock;
63 struct bin_attribute bin;
64
65 u8 *writebuf;
66 unsigned write_max;
67 unsigned num_addresses;
68
69 /*
70 * Some chips tie up multiple I2C addresses; dummy devices reserve
71 * them for us, and we'll use them with SMBus calls.
72 */
73 struct i2c_client *client[];
74};
75
76/*
77 * This parameter is to help this driver avoid blocking other drivers out
78 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
79 * clock, one 256 byte read takes about 1/43 second which is excessive;
80 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
81 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
82 *
83 * This value is forced to be a power of two so that writes align on pages.
84 */
85static unsigned io_limit = 128;
86module_param(io_limit, uint, 0);
87MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
88
89/*
90 * Specs often allow 5 msec for a page write, sometimes 20 msec;
91 * it's important to recover from write timeouts.
92 */
93static unsigned write_timeout = 25;
94module_param(write_timeout, uint, 0);
95MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
96
97#define AT24_SIZE_BYTELEN 5
98#define AT24_SIZE_FLAGS 8
99
100#define AT24_BITMASK(x) (BIT(x) - 1)
101
102/* create non-zero magic value for given eeprom parameters */
103#define AT24_DEVICE_MAGIC(_len, _flags) \
104 ((1 << AT24_SIZE_FLAGS | (_flags)) \
105 << AT24_SIZE_BYTELEN | ilog2(_len))
106
107static const struct i2c_device_id at24_ids[] = {
108 /* needs 8 addresses as A0-A2 are ignored */
109 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
110 /* old variants can't be handled with this generic entry! */
111 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
112 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
113 /* spd is a 24c02 in memory DIMMs */
114 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
115 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
116 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
117 /* 24rf08 quirk is handled at i2c-core */
118 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
119 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
120 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
121 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
122 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
123 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
124 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
125 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
126 { "at24", 0 },
127 { /* END OF LIST */ }
128};
129MODULE_DEVICE_TABLE(i2c, at24_ids);
130
131/*-------------------------------------------------------------------------*/
132
133/*
134 * This routine supports chips which consume multiple I2C addresses. It
135 * computes the addressing information to be used for a given r/w request.
136 * Assumes that sanity checks for offset happened at sysfs-layer.
137 */
138static struct i2c_client *at24_translate_offset(struct at24_data *at24,
139 unsigned *offset)
140{
141 unsigned i;
142
143 if (at24->chip.flags & AT24_FLAG_ADDR16) {
144 i = *offset >> 16;
145 *offset &= 0xffff;
146 } else {
147 i = *offset >> 8;
148 *offset &= 0xff;
149 }
150
151 return at24->client[i];
152}
153
154static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
155 unsigned offset, size_t count)
156{
157 struct i2c_msg msg[2];
158 u8 msgbuf[2];
159 struct i2c_client *client;
160 int status, i;
161
162 memset(msg, 0, sizeof(msg));
163
164 /*
165 * REVISIT some multi-address chips don't rollover page reads to
166 * the next slave address, so we may need to truncate the count.
167 * Those chips might need another quirk flag.
168 *
169 * If the real hardware used four adjacent 24c02 chips and that
170 * were misconfigured as one 24c08, that would be a similar effect:
171 * one "eeprom" file not four, but larger reads would fail when
172 * they crossed certain pages.
173 */
174
175 /*
176 * Slave address and byte offset derive from the offset. Always
177 * set the byte address; on a multi-master board, another master
178 * may have changed the chip's "current" address pointer.
179 */
180 client = at24_translate_offset(at24, &offset);
181
182 if (count > io_limit)
183 count = io_limit;
184
185 /* Smaller eeproms can work given some SMBus extension calls */
186 if (at24->use_smbus) {
187 if (count > I2C_SMBUS_BLOCK_MAX)
188 count = I2C_SMBUS_BLOCK_MAX;
189 status = i2c_smbus_read_i2c_block_data(client, offset,
190 count, buf);
191 dev_dbg(&client->dev, "smbus read %zu@%d --> %d\n",
192 count, offset, status);
193 return (status < 0) ? -EIO : status;
194 }
195
196 /*
197 * When we have a better choice than SMBus calls, use a combined
198 * I2C message. Write address; then read up to io_limit data bytes.
199 * Note that read page rollover helps us here (unlike writes).
200 * msgbuf is u8 and will cast to our needs.
201 */
202 i = 0;
203 if (at24->chip.flags & AT24_FLAG_ADDR16)
204 msgbuf[i++] = offset >> 8;
205 msgbuf[i++] = offset;
206
207 msg[0].addr = client->addr;
208 msg[0].buf = msgbuf;
209 msg[0].len = i;
210
211 msg[1].addr = client->addr;
212 msg[1].flags = I2C_M_RD;
213 msg[1].buf = buf;
214 msg[1].len = count;
215
216 status = i2c_transfer(client->adapter, msg, 2);
217 dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n",
218 count, offset, status);
219
220 if (status == 2)
221 return count;
222 else if (status >= 0)
223 return -EIO;
224 else
225 return status;
226}
227
228static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
229 char *buf, loff_t off, size_t count)
230{
231 struct at24_data *at24;
232 ssize_t retval = 0;
233
234 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
235
236 if (unlikely(!count))
237 return count;
238
239 /*
240 * Read data from chip, protecting against concurrent updates
241 * from this host, but not from other I2C masters.
242 */
243 mutex_lock(&at24->lock);
244
245 while (count) {
246 ssize_t status;
247
248 status = at24_eeprom_read(at24, buf, off, count);
249 if (status <= 0) {
250 if (retval == 0)
251 retval = status;
252 break;
253 }
254 buf += status;
255 off += status;
256 count -= status;
257 retval += status;
258 }
259
260 mutex_unlock(&at24->lock);
261
262 return retval;
263}
264
265
266/*
267 * REVISIT: export at24_bin{read,write}() to let other kernel code use
268 * eeprom data. For example, it might hold a board's Ethernet address, or
269 * board-specific calibration data generated on the manufacturing floor.
270 */
271
272
273/*
274 * Note that if the hardware write-protect pin is pulled high, the whole
275 * chip is normally write protected. But there are plenty of product
276 * variants here, including OTP fuses and partial chip protect.
277 *
278 * We only use page mode writes; the alternative is sloooow. This routine
279 * writes at most one page.
280 */
281static ssize_t at24_eeprom_write(struct at24_data *at24, char *buf,
282 unsigned offset, size_t count)
283{
284 struct i2c_client *client;
285 struct i2c_msg msg;
286 ssize_t status;
287 unsigned long timeout, write_time;
288 unsigned next_page;
289
290 /* Get corresponding I2C address and adjust offset */
291 client = at24_translate_offset(at24, &offset);
292
293 /* write_max is at most a page */
294 if (count > at24->write_max)
295 count = at24->write_max;
296
297 /* Never roll over backwards, to the start of this page */
298 next_page = roundup(offset + 1, at24->chip.page_size);
299 if (offset + count > next_page)
300 count = next_page - offset;
301
302 /* If we'll use I2C calls for I/O, set up the message */
303 if (!at24->use_smbus) {
304 int i = 0;
305
306 msg.addr = client->addr;
307 msg.flags = 0;
308
309 /* msg.buf is u8 and casts will mask the values */
310 msg.buf = at24->writebuf;
311 if (at24->chip.flags & AT24_FLAG_ADDR16)
312 msg.buf[i++] = offset >> 8;
313
314 msg.buf[i++] = offset;
315 memcpy(&msg.buf[i], buf, count);
316 msg.len = i + count;
317 }
318
319 /*
320 * Writes fail if the previous one didn't complete yet. We may
321 * loop a few times until this one succeeds, waiting at least
322 * long enough for one entire page write to work.
323 */
324 timeout = jiffies + msecs_to_jiffies(write_timeout);
325 do {
326 write_time = jiffies;
327 if (at24->use_smbus) {
328 status = i2c_smbus_write_i2c_block_data(client,
329 offset, count, buf);
330 if (status == 0)
331 status = count;
332 } else {
333 status = i2c_transfer(client->adapter, &msg, 1);
334 if (status == 1)
335 status = count;
336 }
337 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
338 count, offset, status, jiffies);
339
340 if (status == count)
341 return count;
342
343 /* REVISIT: at HZ=100, this is sloooow */
344 msleep(1);
345 } while (time_before(write_time, timeout));
346
347 return -ETIMEDOUT;
348}
349
350static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
351 char *buf, loff_t off, size_t count)
352{
353 struct at24_data *at24;
354 ssize_t retval = 0;
355
356 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
357
358 if (unlikely(!count))
359 return count;
360
361 /*
362 * Write data to chip, protecting against concurrent updates
363 * from this host, but not from other I2C masters.
364 */
365 mutex_lock(&at24->lock);
366
367 while (count) {
368 ssize_t status;
369
370 status = at24_eeprom_write(at24, buf, off, count);
371 if (status <= 0) {
372 if (retval == 0)
373 retval = status;
374 break;
375 }
376 buf += status;
377 off += status;
378 count -= status;
379 retval += status;
380 }
381
382 mutex_unlock(&at24->lock);
383
384 return retval;
385}
386
387/*-------------------------------------------------------------------------*/
388
389static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
390{
391 struct at24_platform_data chip;
392 bool writable;
393 bool use_smbus = false;
394 struct at24_data *at24;
395 int err;
396 unsigned i, num_addresses;
397 kernel_ulong_t magic;
398
399 if (client->dev.platform_data) {
400 chip = *(struct at24_platform_data *)client->dev.platform_data;
401 } else {
402 if (!id->driver_data) {
403 err = -ENODEV;
404 goto err_out;
405 }
406 magic = id->driver_data;
407 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
408 magic >>= AT24_SIZE_BYTELEN;
409 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
410 /*
411 * This is slow, but we can't know all eeproms, so we better
412 * play safe. Specifying custom eeprom-types via platform_data
413 * is recommended anyhow.
414 */
415 chip.page_size = 1;
416 }
417
418 if (!is_power_of_2(chip.byte_len))
419 dev_warn(&client->dev,
420 "byte_len looks suspicious (no power of 2)!\n");
421 if (!is_power_of_2(chip.page_size))
422 dev_warn(&client->dev,
423 "page_size looks suspicious (no power of 2)!\n");
424
425 /* Use I2C operations unless we're stuck with SMBus extensions. */
426 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
427 if (chip.flags & AT24_FLAG_ADDR16) {
428 err = -EPFNOSUPPORT;
429 goto err_out;
430 }
431 if (!i2c_check_functionality(client->adapter,
432 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
433 err = -EPFNOSUPPORT;
434 goto err_out;
435 }
436 use_smbus = true;
437 }
438
439 if (chip.flags & AT24_FLAG_TAKE8ADDR)
440 num_addresses = 8;
441 else
442 num_addresses = DIV_ROUND_UP(chip.byte_len,
443 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
444
445 at24 = kzalloc(sizeof(struct at24_data) +
446 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
447 if (!at24) {
448 err = -ENOMEM;
449 goto err_out;
450 }
451
452 mutex_init(&at24->lock);
453 at24->use_smbus = use_smbus;
454 at24->chip = chip;
455 at24->num_addresses = num_addresses;
456
457 /*
458 * Export the EEPROM bytes through sysfs, since that's convenient.
459 * By default, only root should see the data (maybe passwords etc)
460 */
461 at24->bin.attr.name = "eeprom";
462 at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
463 at24->bin.read = at24_bin_read;
464 at24->bin.size = chip.byte_len;
465
466 writable = !(chip.flags & AT24_FLAG_READONLY);
467 if (writable) {
468 if (!use_smbus || i2c_check_functionality(client->adapter,
469 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
470
471 unsigned write_max = chip.page_size;
472
473 at24->bin.write = at24_bin_write;
474 at24->bin.attr.mode |= S_IWUSR;
475
476 if (write_max > io_limit)
477 write_max = io_limit;
478 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
479 write_max = I2C_SMBUS_BLOCK_MAX;
480 at24->write_max = write_max;
481
482 /* buffer (data + address at the beginning) */
483 at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL);
484 if (!at24->writebuf) {
485 err = -ENOMEM;
486 goto err_struct;
487 }
488 } else {
489 dev_warn(&client->dev,
490 "cannot write due to controller restrictions.");
491 }
492 }
493
494 at24->client[0] = client;
495
496 /* use dummy devices for multiple-address chips */
497 for (i = 1; i < num_addresses; i++) {
498 at24->client[i] = i2c_new_dummy(client->adapter,
499 client->addr + i);
500 if (!at24->client[i]) {
501 dev_err(&client->dev, "address 0x%02x unavailable\n",
502 client->addr + i);
503 err = -EADDRINUSE;
504 goto err_clients;
505 }
506 }
507
508 err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
509 if (err)
510 goto err_clients;
511
512 i2c_set_clientdata(client, at24);
513
514 dev_info(&client->dev, "%zu byte %s EEPROM %s\n",
515 at24->bin.size, client->name,
516 writable ? "(writable)" : "(read-only)");
517 dev_dbg(&client->dev,
518 "page_size %d, num_addresses %d, write_max %d%s\n",
519 chip.page_size, num_addresses,
520 at24->write_max,
521 use_smbus ? ", use_smbus" : "");
522
523 return 0;
524
525err_clients:
526 for (i = 1; i < num_addresses; i++)
527 if (at24->client[i])
528 i2c_unregister_device(at24->client[i]);
529
530 kfree(at24->writebuf);
531err_struct:
532 kfree(at24);
533err_out:
534 dev_dbg(&client->dev, "probe error %d\n", err);
535 return err;
536}
537
538static int __devexit at24_remove(struct i2c_client *client)
539{
540 struct at24_data *at24;
541 int i;
542
543 at24 = i2c_get_clientdata(client);
544 sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
545
546 for (i = 1; i < at24->num_addresses; i++)
547 i2c_unregister_device(at24->client[i]);
548
549 kfree(at24->writebuf);
550 kfree(at24);
551 i2c_set_clientdata(client, NULL);
552 return 0;
553}
554
555/*-------------------------------------------------------------------------*/
556
557static struct i2c_driver at24_driver = {
558 .driver = {
559 .name = "at24",
560 .owner = THIS_MODULE,
561 },
562 .probe = at24_probe,
563 .remove = __devexit_p(at24_remove),
564 .id_table = at24_ids,
565};
566
567static int __init at24_init(void)
568{
569 io_limit = rounddown_pow_of_two(io_limit);
570 return i2c_add_driver(&at24_driver);
571}
572module_init(at24_init);
573
574static void __exit at24_exit(void)
575{
576 i2c_del_driver(&at24_driver);
577}
578module_exit(at24_exit);
579
580MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
581MODULE_AUTHOR("David Brownell and Wolfram Sang");
582MODULE_LICENSE("GPL");