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/mod_devicetable.h>
19 #include <linux/log2.h>
20 #include <linux/bitops.h>
21 #include <linux/jiffies.h>
23 #include <linux/acpi.h>
24 #include <linux/i2c.h>
25 #include <linux/nvmem-provider.h>
26 #include <linux/platform_data/at24.h>
29 * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
30 * Differences between different vendor product lines (like Atmel AT24C or
31 * MicroChip 24LC, etc) won't much matter for typical read/write access.
32 * There are also I2C RAM chips, likewise interchangeable. One example
33 * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
35 * However, misconfiguration can lose data. "Set 16-bit memory address"
36 * to a part with 8-bit addressing will overwrite data. Writing with too
37 * big a page size also loses data. And it's not safe to assume that the
38 * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
39 * uses 0x51, for just one example.
41 * Accordingly, explicit board-specific configuration data should be used
42 * in almost all cases. (One partial exception is an SMBus used to access
43 * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
45 * So this driver uses "new style" I2C driver binding, expecting to be
46 * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
47 * similar kernel-resident tables; or, configuration data coming from
50 * Other than binding model, current differences from "eeprom" driver are
51 * that this one handles write access and isn't restricted to 24c02 devices.
52 * It also handles larger devices (32 kbit and up) with two-byte addresses,
53 * which won't work on pure SMBus systems.
57 struct at24_platform_data chip;
61 ssize_t (*read_func)(struct at24_data *, char *, unsigned int, size_t);
62 ssize_t (*write_func)(struct at24_data *,
63 const char *, unsigned int, size_t);
66 * Lock protects against activities from other Linux tasks,
67 * but not from changes by other I2C masters.
73 unsigned num_addresses;
75 struct nvmem_config nvmem_config;
76 struct nvmem_device *nvmem;
79 * Some chips tie up multiple I2C addresses; dummy devices reserve
80 * them for us, and we'll use them with SMBus calls.
82 struct i2c_client *client[];
86 * This parameter is to help this driver avoid blocking other drivers out
87 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
88 * clock, one 256 byte read takes about 1/43 second which is excessive;
89 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
90 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
92 * This value is forced to be a power of two so that writes align on pages.
94 static unsigned io_limit = 128;
95 module_param(io_limit, uint, 0);
96 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
99 * Specs often allow 5 msec for a page write, sometimes 20 msec;
100 * it's important to recover from write timeouts.
102 static unsigned write_timeout = 25;
103 module_param(write_timeout, uint, 0);
104 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
106 #define AT24_SIZE_BYTELEN 5
107 #define AT24_SIZE_FLAGS 8
109 #define AT24_BITMASK(x) (BIT(x) - 1)
111 /* create non-zero magic value for given eeprom parameters */
112 #define AT24_DEVICE_MAGIC(_len, _flags) \
113 ((1 << AT24_SIZE_FLAGS | (_flags)) \
114 << AT24_SIZE_BYTELEN | ilog2(_len))
117 * Both reads and writes fail if the previous write didn't complete yet. This
118 * macro loops a few times waiting at least long enough for one entire page
121 * It takes two parameters: a variable in which the future timeout in jiffies
122 * will be stored and a temporary variable holding the time of the last
123 * iteration of processing the request. Both should be unsigned integers
124 * holding at least 32 bits.
126 #define loop_until_timeout(tout, op_time) \
127 for (tout = jiffies + msecs_to_jiffies(write_timeout), \
129 time_before(op_time, tout); \
130 usleep_range(1000, 1500), op_time = jiffies)
132 static const struct i2c_device_id at24_ids[] = {
133 /* needs 8 addresses as A0-A2 are ignored */
134 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
135 /* old variants can't be handled with this generic entry! */
136 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
137 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
138 /* spd is a 24c02 in memory DIMMs */
139 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
140 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
141 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
142 /* 24rf08 quirk is handled at i2c-core */
143 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
144 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
145 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
146 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
147 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
148 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
149 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
150 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
152 { /* END OF LIST */ }
154 MODULE_DEVICE_TABLE(i2c, at24_ids);
156 static const struct acpi_device_id at24_acpi_ids[] = {
157 { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
160 MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
162 /*-------------------------------------------------------------------------*/
165 * This routine supports chips which consume multiple I2C addresses. It
166 * computes the addressing information to be used for a given r/w request.
167 * Assumes that sanity checks for offset happened at sysfs-layer.
169 * Slave address and byte offset derive from the offset. Always
170 * set the byte address; on a multi-master board, another master
171 * may have changed the chip's "current" address pointer.
173 * REVISIT some multi-address chips don't rollover page reads to
174 * the next slave address, so we may need to truncate the count.
175 * Those chips might need another quirk flag.
177 * If the real hardware used four adjacent 24c02 chips and that
178 * were misconfigured as one 24c08, that would be a similar effect:
179 * one "eeprom" file not four, but larger reads would fail when
180 * they crossed certain pages.
182 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
183 unsigned int *offset)
187 if (at24->chip.flags & AT24_FLAG_ADDR16) {
195 return at24->client[i];
198 static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf,
199 unsigned int offset, size_t count)
201 unsigned long timeout, read_time;
202 struct i2c_client *client;
205 client = at24_translate_offset(at24, &offset);
207 if (count > io_limit)
210 /* Smaller eeproms can work given some SMBus extension calls */
211 if (count > I2C_SMBUS_BLOCK_MAX)
212 count = I2C_SMBUS_BLOCK_MAX;
214 loop_until_timeout(timeout, read_time) {
215 status = i2c_smbus_read_i2c_block_data_or_emulated(client,
219 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
220 count, offset, status, jiffies);
229 static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
230 unsigned int offset, size_t count)
232 unsigned long timeout, read_time;
233 struct i2c_client *client;
234 struct i2c_msg msg[2];
238 memset(msg, 0, sizeof(msg));
239 client = at24_translate_offset(at24, &offset);
241 if (count > io_limit)
245 * When we have a better choice than SMBus calls, use a combined I2C
246 * message. Write address; then read up to io_limit data bytes. Note
247 * that read page rollover helps us here (unlike writes). msgbuf is
248 * u8 and will cast to our needs.
251 if (at24->chip.flags & AT24_FLAG_ADDR16)
252 msgbuf[i++] = offset >> 8;
253 msgbuf[i++] = offset;
255 msg[0].addr = client->addr;
259 msg[1].addr = client->addr;
260 msg[1].flags = I2C_M_RD;
264 loop_until_timeout(timeout, read_time) {
265 status = i2c_transfer(client->adapter, msg, 2);
269 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
270 count, offset, status, jiffies);
280 * Note that if the hardware write-protect pin is pulled high, the whole
281 * chip is normally write protected. But there are plenty of product
282 * variants here, including OTP fuses and partial chip protect.
284 * We only use page mode writes; the alternative is sloooow. This routine
285 * writes at most one page.
287 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
288 unsigned int offset, size_t count)
290 struct i2c_client *client;
293 unsigned long timeout, write_time;
296 /* Get corresponding I2C address and adjust offset */
297 client = at24_translate_offset(at24, &offset);
299 /* write_max is at most a page */
300 if (count > at24->write_max)
301 count = at24->write_max;
303 /* Never roll over backwards, to the start of this page */
304 next_page = roundup(offset + 1, at24->chip.page_size);
305 if (offset + count > next_page)
306 count = next_page - offset;
308 /* If we'll use I2C calls for I/O, set up the message */
309 if (!at24->use_smbus) {
312 msg.addr = client->addr;
315 /* msg.buf is u8 and casts will mask the values */
316 msg.buf = at24->writebuf;
317 if (at24->chip.flags & AT24_FLAG_ADDR16)
318 msg.buf[i++] = offset >> 8;
320 msg.buf[i++] = offset;
321 memcpy(&msg.buf[i], buf, count);
325 loop_until_timeout(timeout, write_time) {
326 if (at24->use_smbus_write) {
327 switch (at24->use_smbus_write) {
328 case I2C_SMBUS_I2C_BLOCK_DATA:
329 status = i2c_smbus_write_i2c_block_data(client,
332 case I2C_SMBUS_BYTE_DATA:
333 status = i2c_smbus_write_byte_data(client,
341 status = i2c_transfer(client->adapter, &msg, 1);
345 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
346 count, offset, status, jiffies);
355 static int at24_read(void *priv, unsigned int off, void *val, size_t count)
357 struct at24_data *at24 = priv;
360 if (unlikely(!count))
364 * Read data from chip, protecting against concurrent updates
365 * from this host, but not from other I2C masters.
367 mutex_lock(&at24->lock);
372 status = at24->read_func(at24, buf, off, count);
374 mutex_unlock(&at24->lock);
382 mutex_unlock(&at24->lock);
387 static int at24_write(void *priv, unsigned int off, void *val, size_t count)
389 struct at24_data *at24 = priv;
392 if (unlikely(!count))
396 * Write data to chip, protecting against concurrent updates
397 * from this host, but not from other I2C masters.
399 mutex_lock(&at24->lock);
404 status = at24->write_func(at24, buf, off, count);
406 mutex_unlock(&at24->lock);
414 mutex_unlock(&at24->lock);
420 static void at24_get_ofdata(struct i2c_client *client,
421 struct at24_platform_data *chip)
424 struct device_node *node = client->dev.of_node;
427 if (of_get_property(node, "read-only", NULL))
428 chip->flags |= AT24_FLAG_READONLY;
429 val = of_get_property(node, "pagesize", NULL);
431 chip->page_size = be32_to_cpup(val);
435 static void at24_get_ofdata(struct i2c_client *client,
436 struct at24_platform_data *chip)
438 #endif /* CONFIG_OF */
440 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
442 struct at24_platform_data chip;
443 kernel_ulong_t magic = 0;
446 int use_smbus_write = 0;
447 struct at24_data *at24;
449 unsigned i, num_addresses;
451 if (client->dev.platform_data) {
452 chip = *(struct at24_platform_data *)client->dev.platform_data;
455 magic = id->driver_data;
457 const struct acpi_device_id *aid;
459 aid = acpi_match_device(at24_acpi_ids, &client->dev);
461 magic = aid->driver_data;
466 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
467 magic >>= AT24_SIZE_BYTELEN;
468 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
470 * This is slow, but we can't know all eeproms, so we better
471 * play safe. Specifying custom eeprom-types via platform_data
472 * is recommended anyhow.
476 /* update chipdata if OF is present */
477 at24_get_ofdata(client, &chip);
483 if (!is_power_of_2(chip.byte_len))
484 dev_warn(&client->dev,
485 "byte_len looks suspicious (no power of 2)!\n");
486 if (!chip.page_size) {
487 dev_err(&client->dev, "page_size must not be 0!\n");
490 if (!is_power_of_2(chip.page_size))
491 dev_warn(&client->dev,
492 "page_size looks suspicious (no power of 2)!\n");
494 /* Use I2C operations unless we're stuck with SMBus extensions. */
495 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
496 if (chip.flags & AT24_FLAG_ADDR16)
497 return -EPFNOSUPPORT;
499 if (i2c_check_functionality(client->adapter,
500 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
501 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
502 } else if (i2c_check_functionality(client->adapter,
503 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
504 use_smbus = I2C_SMBUS_WORD_DATA;
505 } else if (i2c_check_functionality(client->adapter,
506 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
507 use_smbus = I2C_SMBUS_BYTE_DATA;
509 return -EPFNOSUPPORT;
512 if (i2c_check_functionality(client->adapter,
513 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
514 use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
515 } else if (i2c_check_functionality(client->adapter,
516 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
517 use_smbus_write = I2C_SMBUS_BYTE_DATA;
522 if (chip.flags & AT24_FLAG_TAKE8ADDR)
525 num_addresses = DIV_ROUND_UP(chip.byte_len,
526 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
528 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
529 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
533 mutex_init(&at24->lock);
534 at24->use_smbus = use_smbus;
535 at24->use_smbus_write = use_smbus_write;
537 at24->num_addresses = num_addresses;
539 at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
540 : at24_eeprom_read_i2c;
541 at24->write_func = at24_eeprom_write;
543 writable = !(chip.flags & AT24_FLAG_READONLY);
545 if (!use_smbus || use_smbus_write) {
547 unsigned write_max = chip.page_size;
549 if (write_max > io_limit)
550 write_max = io_limit;
551 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
552 write_max = I2C_SMBUS_BLOCK_MAX;
553 at24->write_max = write_max;
555 /* buffer (data + address at the beginning) */
556 at24->writebuf = devm_kzalloc(&client->dev,
557 write_max + 2, GFP_KERNEL);
561 dev_warn(&client->dev,
562 "cannot write due to controller restrictions.");
566 at24->client[0] = client;
568 /* use dummy devices for multiple-address chips */
569 for (i = 1; i < num_addresses; i++) {
570 at24->client[i] = i2c_new_dummy(client->adapter,
572 if (!at24->client[i]) {
573 dev_err(&client->dev, "address 0x%02x unavailable\n",
580 at24->nvmem_config.name = dev_name(&client->dev);
581 at24->nvmem_config.dev = &client->dev;
582 at24->nvmem_config.read_only = !writable;
583 at24->nvmem_config.root_only = true;
584 at24->nvmem_config.owner = THIS_MODULE;
585 at24->nvmem_config.compat = true;
586 at24->nvmem_config.base_dev = &client->dev;
587 at24->nvmem_config.reg_read = at24_read;
588 at24->nvmem_config.reg_write = at24_write;
589 at24->nvmem_config.priv = at24;
590 at24->nvmem_config.stride = 4;
591 at24->nvmem_config.word_size = 1;
592 at24->nvmem_config.size = chip.byte_len;
594 at24->nvmem = nvmem_register(&at24->nvmem_config);
596 if (IS_ERR(at24->nvmem)) {
597 err = PTR_ERR(at24->nvmem);
601 i2c_set_clientdata(client, at24);
603 dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
604 chip.byte_len, client->name,
605 writable ? "writable" : "read-only", at24->write_max);
606 if (use_smbus == I2C_SMBUS_WORD_DATA ||
607 use_smbus == I2C_SMBUS_BYTE_DATA) {
608 dev_notice(&client->dev, "Falling back to %s reads, "
609 "performance will suffer\n", use_smbus ==
610 I2C_SMBUS_WORD_DATA ? "word" : "byte");
613 /* export data to kernel code */
615 chip.setup(at24->nvmem, chip.context);
620 for (i = 1; i < num_addresses; i++)
622 i2c_unregister_device(at24->client[i]);
627 static int at24_remove(struct i2c_client *client)
629 struct at24_data *at24;
632 at24 = i2c_get_clientdata(client);
634 nvmem_unregister(at24->nvmem);
636 for (i = 1; i < at24->num_addresses; i++)
637 i2c_unregister_device(at24->client[i]);
642 /*-------------------------------------------------------------------------*/
644 static struct i2c_driver at24_driver = {
647 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
650 .remove = at24_remove,
651 .id_table = at24_ids,
654 static int __init at24_init(void)
657 pr_err("at24: io_limit must not be 0!\n");
661 io_limit = rounddown_pow_of_two(io_limit);
662 return i2c_add_driver(&at24_driver);
664 module_init(at24_init);
666 static void __exit at24_exit(void)
668 i2c_del_driver(&at24_driver);
670 module_exit(at24_exit);
672 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
673 MODULE_AUTHOR("David Brownell and Wolfram Sang");
674 MODULE_LICENSE("GPL");