2 * at24.c - handle most I2C EEPROMs
4 * Copyright (C) 2005-2007 David Brownell
5 * Copyright (C) 2008 Wolfram Sang, Pengutronix
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.
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>
24 #include <linux/i2c.h>
25 #include <linux/platform_data/at24.h>
28 * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
29 * Differences between different vendor product lines (like Atmel AT24C or
30 * MicroChip 24LC, etc) won't much matter for typical read/write access.
31 * There are also I2C RAM chips, likewise interchangeable. One example
32 * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
34 * However, misconfiguration can lose data. "Set 16-bit memory address"
35 * to a part with 8-bit addressing will overwrite data. Writing with too
36 * big a page size also loses data. And it's not safe to assume that the
37 * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
38 * uses 0x51, for just one example.
40 * Accordingly, explicit board-specific configuration data should be used
41 * in almost all cases. (One partial exception is an SMBus used to access
42 * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
44 * So this driver uses "new style" I2C driver binding, expecting to be
45 * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
46 * similar kernel-resident tables; or, configuration data coming from
49 * Other than binding model, current differences from "eeprom" driver are
50 * that this one handles write access and isn't restricted to 24c02 devices.
51 * It also handles larger devices (32 kbit and up) with two-byte addresses,
52 * which won't work on pure SMBus systems.
56 struct at24_platform_data chip;
57 struct memory_accessor macc;
61 * Lock protects against activities from other Linux tasks,
62 * but not from changes by other I2C masters.
65 struct bin_attribute bin;
69 unsigned num_addresses;
72 * Some chips tie up multiple I2C addresses; dummy devices reserve
73 * them for us, and we'll use them with SMBus calls.
75 struct i2c_client *client[];
79 * This parameter is to help this driver avoid blocking other drivers out
80 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
81 * clock, one 256 byte read takes about 1/43 second which is excessive;
82 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
83 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
85 * This value is forced to be a power of two so that writes align on pages.
87 static unsigned io_limit = 128;
88 module_param(io_limit, uint, 0);
89 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
92 * Specs often allow 5 msec for a page write, sometimes 20 msec;
93 * it's important to recover from write timeouts.
95 static unsigned write_timeout = 25;
96 module_param(write_timeout, uint, 0);
97 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
99 #define AT24_SIZE_BYTELEN 5
100 #define AT24_SIZE_FLAGS 8
102 #define AT24_BITMASK(x) (BIT(x) - 1)
104 /* create non-zero magic value for given eeprom parameters */
105 #define AT24_DEVICE_MAGIC(_len, _flags) \
106 ((1 << AT24_SIZE_FLAGS | (_flags)) \
107 << AT24_SIZE_BYTELEN | ilog2(_len))
109 static const struct i2c_device_id at24_ids[] = {
110 /* needs 8 addresses as A0-A2 are ignored */
111 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
112 /* old variants can't be handled with this generic entry! */
113 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
114 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
115 /* spd is a 24c02 in memory DIMMs */
116 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
117 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
118 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
119 /* 24rf08 quirk is handled at i2c-core */
120 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
121 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
122 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
123 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
124 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
125 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
126 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
127 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
129 { /* END OF LIST */ }
131 MODULE_DEVICE_TABLE(i2c, at24_ids);
133 /*-------------------------------------------------------------------------*/
136 * This routine supports chips which consume multiple I2C addresses. It
137 * computes the addressing information to be used for a given r/w request.
138 * Assumes that sanity checks for offset happened at sysfs-layer.
140 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
145 if (at24->chip.flags & AT24_FLAG_ADDR16) {
153 return at24->client[i];
156 static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
157 unsigned offset, size_t count)
159 struct i2c_msg msg[2];
161 struct i2c_client *client;
162 unsigned long timeout, read_time;
165 memset(msg, 0, sizeof(msg));
168 * REVISIT some multi-address chips don't rollover page reads to
169 * the next slave address, so we may need to truncate the count.
170 * Those chips might need another quirk flag.
172 * If the real hardware used four adjacent 24c02 chips and that
173 * were misconfigured as one 24c08, that would be a similar effect:
174 * one "eeprom" file not four, but larger reads would fail when
175 * they crossed certain pages.
179 * Slave address and byte offset derive from the offset. Always
180 * set the byte address; on a multi-master board, another master
181 * may have changed the chip's "current" address pointer.
183 client = at24_translate_offset(at24, &offset);
185 if (count > io_limit)
188 switch (at24->use_smbus) {
189 case I2C_SMBUS_I2C_BLOCK_DATA:
190 /* Smaller eeproms can work given some SMBus extension calls */
191 if (count > I2C_SMBUS_BLOCK_MAX)
192 count = I2C_SMBUS_BLOCK_MAX;
194 case I2C_SMBUS_WORD_DATA:
197 case I2C_SMBUS_BYTE_DATA:
202 * When we have a better choice than SMBus calls, use a
203 * combined I2C message. Write address; then read up to
204 * io_limit data bytes. Note that read page rollover helps us
205 * here (unlike writes). msgbuf is u8 and will cast to our
209 if (at24->chip.flags & AT24_FLAG_ADDR16)
210 msgbuf[i++] = offset >> 8;
211 msgbuf[i++] = offset;
213 msg[0].addr = client->addr;
217 msg[1].addr = client->addr;
218 msg[1].flags = I2C_M_RD;
224 * Reads fail if the previous write didn't complete yet. We may
225 * loop a few times until this one succeeds, waiting at least
226 * long enough for one entire page write to work.
228 timeout = jiffies + msecs_to_jiffies(write_timeout);
231 switch (at24->use_smbus) {
232 case I2C_SMBUS_I2C_BLOCK_DATA:
233 status = i2c_smbus_read_i2c_block_data(client, offset,
236 case I2C_SMBUS_WORD_DATA:
237 status = i2c_smbus_read_word_data(client, offset);
239 buf[0] = status & 0xff;
240 buf[1] = status >> 8;
244 case I2C_SMBUS_BYTE_DATA:
245 status = i2c_smbus_read_byte_data(client, offset);
252 status = i2c_transfer(client->adapter, msg, 2);
256 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
257 count, offset, status, jiffies);
262 /* REVISIT: at HZ=100, this is sloooow */
264 } while (time_before(read_time, timeout));
269 static ssize_t at24_read(struct at24_data *at24,
270 char *buf, loff_t off, size_t count)
274 if (unlikely(!count))
278 * Read data from chip, protecting against concurrent updates
279 * from this host, but not from other I2C masters.
281 mutex_lock(&at24->lock);
286 status = at24_eeprom_read(at24, buf, off, count);
298 mutex_unlock(&at24->lock);
303 static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
304 struct bin_attribute *attr,
305 char *buf, loff_t off, size_t count)
307 struct at24_data *at24;
309 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
310 return at24_read(at24, buf, off, count);
315 * Note that if the hardware write-protect pin is pulled high, the whole
316 * chip is normally write protected. But there are plenty of product
317 * variants here, including OTP fuses and partial chip protect.
319 * We only use page mode writes; the alternative is sloooow. This routine
320 * writes at most one page.
322 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
323 unsigned offset, size_t count)
325 struct i2c_client *client;
328 unsigned long timeout, write_time;
331 /* Get corresponding I2C address and adjust offset */
332 client = at24_translate_offset(at24, &offset);
334 /* write_max is at most a page */
335 if (count > at24->write_max)
336 count = at24->write_max;
338 /* Never roll over backwards, to the start of this page */
339 next_page = roundup(offset + 1, at24->chip.page_size);
340 if (offset + count > next_page)
341 count = next_page - offset;
343 /* If we'll use I2C calls for I/O, set up the message */
344 if (!at24->use_smbus) {
347 msg.addr = client->addr;
350 /* msg.buf is u8 and casts will mask the values */
351 msg.buf = at24->writebuf;
352 if (at24->chip.flags & AT24_FLAG_ADDR16)
353 msg.buf[i++] = offset >> 8;
355 msg.buf[i++] = offset;
356 memcpy(&msg.buf[i], buf, count);
361 * Writes fail if the previous one didn't complete yet. We may
362 * loop a few times until this one succeeds, waiting at least
363 * long enough for one entire page write to work.
365 timeout = jiffies + msecs_to_jiffies(write_timeout);
367 write_time = jiffies;
368 if (at24->use_smbus) {
369 status = i2c_smbus_write_i2c_block_data(client,
374 status = i2c_transfer(client->adapter, &msg, 1);
378 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
379 count, offset, status, jiffies);
384 /* REVISIT: at HZ=100, this is sloooow */
386 } while (time_before(write_time, timeout));
391 static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
396 if (unlikely(!count))
400 * Write data to chip, protecting against concurrent updates
401 * from this host, but not from other I2C masters.
403 mutex_lock(&at24->lock);
408 status = at24_eeprom_write(at24, buf, off, count);
420 mutex_unlock(&at24->lock);
425 static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
426 struct bin_attribute *attr,
427 char *buf, loff_t off, size_t count)
429 struct at24_data *at24;
431 if (unlikely(off >= attr->size))
434 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
435 return at24_write(at24, buf, off, count);
438 /*-------------------------------------------------------------------------*/
441 * This lets other kernel code access the eeprom data. For example, it
442 * might hold a board's Ethernet address, or board-specific calibration
443 * data generated on the manufacturing floor.
446 static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
447 off_t offset, size_t count)
449 struct at24_data *at24 = container_of(macc, struct at24_data, macc);
451 return at24_read(at24, buf, offset, count);
454 static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
455 off_t offset, size_t count)
457 struct at24_data *at24 = container_of(macc, struct at24_data, macc);
459 return at24_write(at24, buf, offset, count);
462 /*-------------------------------------------------------------------------*/
465 static void at24_get_ofdata(struct i2c_client *client,
466 struct at24_platform_data *chip)
469 struct device_node *node = client->dev.of_node;
472 if (of_get_property(node, "read-only", NULL))
473 chip->flags |= AT24_FLAG_READONLY;
474 val = of_get_property(node, "pagesize", NULL);
476 chip->page_size = be32_to_cpup(val);
480 static void at24_get_ofdata(struct i2c_client *client,
481 struct at24_platform_data *chip)
483 #endif /* CONFIG_OF */
485 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
487 struct at24_platform_data chip;
490 struct at24_data *at24;
492 unsigned i, num_addresses;
493 kernel_ulong_t magic;
495 if (client->dev.platform_data) {
496 chip = *(struct at24_platform_data *)client->dev.platform_data;
498 if (!id->driver_data)
501 magic = id->driver_data;
502 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
503 magic >>= AT24_SIZE_BYTELEN;
504 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
506 * This is slow, but we can't know all eeproms, so we better
507 * play safe. Specifying custom eeprom-types via platform_data
508 * is recommended anyhow.
512 /* update chipdata if OF is present */
513 at24_get_ofdata(client, &chip);
519 if (!is_power_of_2(chip.byte_len))
520 dev_warn(&client->dev,
521 "byte_len looks suspicious (no power of 2)!\n");
522 if (!chip.page_size) {
523 dev_err(&client->dev, "page_size must not be 0!\n");
526 if (!is_power_of_2(chip.page_size))
527 dev_warn(&client->dev,
528 "page_size looks suspicious (no power of 2)!\n");
530 /* Use I2C operations unless we're stuck with SMBus extensions. */
531 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
532 if (chip.flags & AT24_FLAG_ADDR16)
533 return -EPFNOSUPPORT;
535 if (i2c_check_functionality(client->adapter,
536 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
537 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
538 } else if (i2c_check_functionality(client->adapter,
539 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
540 use_smbus = I2C_SMBUS_WORD_DATA;
541 } else if (i2c_check_functionality(client->adapter,
542 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
543 use_smbus = I2C_SMBUS_BYTE_DATA;
545 return -EPFNOSUPPORT;
549 if (chip.flags & AT24_FLAG_TAKE8ADDR)
552 num_addresses = DIV_ROUND_UP(chip.byte_len,
553 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
555 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
556 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
560 mutex_init(&at24->lock);
561 at24->use_smbus = use_smbus;
563 at24->num_addresses = num_addresses;
566 * Export the EEPROM bytes through sysfs, since that's convenient.
567 * By default, only root should see the data (maybe passwords etc)
569 sysfs_bin_attr_init(&at24->bin);
570 at24->bin.attr.name = "eeprom";
571 at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
572 at24->bin.read = at24_bin_read;
573 at24->bin.size = chip.byte_len;
575 at24->macc.read = at24_macc_read;
577 writable = !(chip.flags & AT24_FLAG_READONLY);
579 if (!use_smbus || i2c_check_functionality(client->adapter,
580 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
582 unsigned write_max = chip.page_size;
584 at24->macc.write = at24_macc_write;
586 at24->bin.write = at24_bin_write;
587 at24->bin.attr.mode |= S_IWUSR;
589 if (write_max > io_limit)
590 write_max = io_limit;
591 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
592 write_max = I2C_SMBUS_BLOCK_MAX;
593 at24->write_max = write_max;
595 /* buffer (data + address at the beginning) */
596 at24->writebuf = devm_kzalloc(&client->dev,
597 write_max + 2, GFP_KERNEL);
601 dev_warn(&client->dev,
602 "cannot write due to controller restrictions.");
606 at24->client[0] = client;
608 /* use dummy devices for multiple-address chips */
609 for (i = 1; i < num_addresses; i++) {
610 at24->client[i] = i2c_new_dummy(client->adapter,
612 if (!at24->client[i]) {
613 dev_err(&client->dev, "address 0x%02x unavailable\n",
620 err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
624 i2c_set_clientdata(client, at24);
626 dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
627 at24->bin.size, client->name,
628 writable ? "writable" : "read-only", at24->write_max);
629 if (use_smbus == I2C_SMBUS_WORD_DATA ||
630 use_smbus == I2C_SMBUS_BYTE_DATA) {
631 dev_notice(&client->dev, "Falling back to %s reads, "
632 "performance will suffer\n", use_smbus ==
633 I2C_SMBUS_WORD_DATA ? "word" : "byte");
636 /* export data to kernel code */
638 chip.setup(&at24->macc, chip.context);
643 for (i = 1; i < num_addresses; i++)
645 i2c_unregister_device(at24->client[i]);
650 static int at24_remove(struct i2c_client *client)
652 struct at24_data *at24;
655 at24 = i2c_get_clientdata(client);
656 sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
658 for (i = 1; i < at24->num_addresses; i++)
659 i2c_unregister_device(at24->client[i]);
664 /*-------------------------------------------------------------------------*/
666 static struct i2c_driver at24_driver = {
669 .owner = THIS_MODULE,
672 .remove = at24_remove,
673 .id_table = at24_ids,
676 static int __init at24_init(void)
679 pr_err("at24: io_limit must not be 0!\n");
683 io_limit = rounddown_pow_of_two(io_limit);
684 return i2c_add_driver(&at24_driver);
686 module_init(at24_init);
688 static void __exit at24_exit(void)
690 i2c_del_driver(&at24_driver);
692 module_exit(at24_exit);
694 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
695 MODULE_AUTHOR("David Brownell and Wolfram Sang");
696 MODULE_LICENSE("GPL");