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. These routines
285 * write at most one page.
288 static size_t at24_adjust_write_count(struct at24_data *at24,
289 unsigned int offset, size_t count)
293 /* write_max is at most a page */
294 if (count > at24->write_max)
295 count = at24->write_max;
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;
305 static ssize_t at24_eeprom_write_smbus_block(struct at24_data *at24,
307 unsigned int offset, size_t count)
309 unsigned long timeout, write_time;
310 struct i2c_client *client;
313 client = at24_translate_offset(at24, &offset);
314 count = at24_adjust_write_count(at24, offset, count);
316 loop_until_timeout(timeout, write_time) {
317 status = i2c_smbus_write_i2c_block_data(client,
322 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
323 count, offset, status, jiffies);
332 static ssize_t at24_eeprom_write_smbus_byte(struct at24_data *at24,
334 unsigned int offset, size_t count)
336 unsigned long timeout, write_time;
337 struct i2c_client *client;
340 client = at24_translate_offset(at24, &offset);
342 loop_until_timeout(timeout, write_time) {
343 status = i2c_smbus_write_byte_data(client, offset, buf[0]);
347 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
348 count, offset, status, jiffies);
357 static ssize_t at24_eeprom_write_i2c(struct at24_data *at24, const char *buf,
358 unsigned int offset, size_t count)
360 unsigned long timeout, write_time;
361 struct i2c_client *client;
366 client = at24_translate_offset(at24, &offset);
367 count = at24_adjust_write_count(at24, offset, count);
369 msg.addr = client->addr;
372 /* msg.buf is u8 and casts will mask the values */
373 msg.buf = at24->writebuf;
374 if (at24->chip.flags & AT24_FLAG_ADDR16)
375 msg.buf[i++] = offset >> 8;
377 msg.buf[i++] = offset;
378 memcpy(&msg.buf[i], buf, count);
381 loop_until_timeout(timeout, write_time) {
382 status = i2c_transfer(client->adapter, &msg, 1);
386 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
387 count, offset, status, jiffies);
396 static int at24_read(void *priv, unsigned int off, void *val, size_t count)
398 struct at24_data *at24 = priv;
401 if (unlikely(!count))
405 * Read data from chip, protecting against concurrent updates
406 * from this host, but not from other I2C masters.
408 mutex_lock(&at24->lock);
413 status = at24->read_func(at24, buf, off, count);
415 mutex_unlock(&at24->lock);
423 mutex_unlock(&at24->lock);
428 static int at24_write(void *priv, unsigned int off, void *val, size_t count)
430 struct at24_data *at24 = priv;
433 if (unlikely(!count))
437 * Write data to chip, protecting against concurrent updates
438 * from this host, but not from other I2C masters.
440 mutex_lock(&at24->lock);
445 status = at24->write_func(at24, buf, off, count);
447 mutex_unlock(&at24->lock);
455 mutex_unlock(&at24->lock);
461 static void at24_get_ofdata(struct i2c_client *client,
462 struct at24_platform_data *chip)
465 struct device_node *node = client->dev.of_node;
468 if (of_get_property(node, "read-only", NULL))
469 chip->flags |= AT24_FLAG_READONLY;
470 val = of_get_property(node, "pagesize", NULL);
472 chip->page_size = be32_to_cpup(val);
476 static void at24_get_ofdata(struct i2c_client *client,
477 struct at24_platform_data *chip)
479 #endif /* CONFIG_OF */
481 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
483 struct at24_platform_data chip;
484 kernel_ulong_t magic = 0;
487 int use_smbus_write = 0;
488 struct at24_data *at24;
490 unsigned i, num_addresses;
492 if (client->dev.platform_data) {
493 chip = *(struct at24_platform_data *)client->dev.platform_data;
496 magic = id->driver_data;
498 const struct acpi_device_id *aid;
500 aid = acpi_match_device(at24_acpi_ids, &client->dev);
502 magic = aid->driver_data;
507 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
508 magic >>= AT24_SIZE_BYTELEN;
509 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
511 * This is slow, but we can't know all eeproms, so we better
512 * play safe. Specifying custom eeprom-types via platform_data
513 * is recommended anyhow.
517 /* update chipdata if OF is present */
518 at24_get_ofdata(client, &chip);
524 if (!is_power_of_2(chip.byte_len))
525 dev_warn(&client->dev,
526 "byte_len looks suspicious (no power of 2)!\n");
527 if (!chip.page_size) {
528 dev_err(&client->dev, "page_size must not be 0!\n");
531 if (!is_power_of_2(chip.page_size))
532 dev_warn(&client->dev,
533 "page_size looks suspicious (no power of 2)!\n");
535 /* Use I2C operations unless we're stuck with SMBus extensions. */
536 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
537 if (chip.flags & AT24_FLAG_ADDR16)
538 return -EPFNOSUPPORT;
540 if (i2c_check_functionality(client->adapter,
541 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
542 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
543 } else if (i2c_check_functionality(client->adapter,
544 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
545 use_smbus = I2C_SMBUS_WORD_DATA;
546 } else if (i2c_check_functionality(client->adapter,
547 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
548 use_smbus = I2C_SMBUS_BYTE_DATA;
550 return -EPFNOSUPPORT;
553 if (i2c_check_functionality(client->adapter,
554 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
555 use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
556 } else if (i2c_check_functionality(client->adapter,
557 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
558 use_smbus_write = I2C_SMBUS_BYTE_DATA;
563 if (chip.flags & AT24_FLAG_TAKE8ADDR)
566 num_addresses = DIV_ROUND_UP(chip.byte_len,
567 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
569 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
570 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
574 mutex_init(&at24->lock);
575 at24->use_smbus = use_smbus;
576 at24->use_smbus_write = use_smbus_write;
578 at24->num_addresses = num_addresses;
580 at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
581 : at24_eeprom_read_i2c;
582 if (at24->use_smbus) {
583 if (at24->use_smbus_write == I2C_SMBUS_I2C_BLOCK_DATA)
584 at24->write_func = at24_eeprom_write_smbus_block;
586 at24->write_func = at24_eeprom_write_smbus_byte;
588 at24->write_func = at24_eeprom_write_i2c;
591 writable = !(chip.flags & AT24_FLAG_READONLY);
593 if (!use_smbus || use_smbus_write) {
595 unsigned write_max = chip.page_size;
597 if (write_max > io_limit)
598 write_max = io_limit;
599 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
600 write_max = I2C_SMBUS_BLOCK_MAX;
601 at24->write_max = write_max;
603 /* buffer (data + address at the beginning) */
604 at24->writebuf = devm_kzalloc(&client->dev,
605 write_max + 2, GFP_KERNEL);
609 dev_warn(&client->dev,
610 "cannot write due to controller restrictions.");
614 at24->client[0] = client;
616 /* use dummy devices for multiple-address chips */
617 for (i = 1; i < num_addresses; i++) {
618 at24->client[i] = i2c_new_dummy(client->adapter,
620 if (!at24->client[i]) {
621 dev_err(&client->dev, "address 0x%02x unavailable\n",
628 at24->nvmem_config.name = dev_name(&client->dev);
629 at24->nvmem_config.dev = &client->dev;
630 at24->nvmem_config.read_only = !writable;
631 at24->nvmem_config.root_only = true;
632 at24->nvmem_config.owner = THIS_MODULE;
633 at24->nvmem_config.compat = true;
634 at24->nvmem_config.base_dev = &client->dev;
635 at24->nvmem_config.reg_read = at24_read;
636 at24->nvmem_config.reg_write = at24_write;
637 at24->nvmem_config.priv = at24;
638 at24->nvmem_config.stride = 4;
639 at24->nvmem_config.word_size = 1;
640 at24->nvmem_config.size = chip.byte_len;
642 at24->nvmem = nvmem_register(&at24->nvmem_config);
644 if (IS_ERR(at24->nvmem)) {
645 err = PTR_ERR(at24->nvmem);
649 i2c_set_clientdata(client, at24);
651 dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
652 chip.byte_len, client->name,
653 writable ? "writable" : "read-only", at24->write_max);
654 if (use_smbus == I2C_SMBUS_WORD_DATA ||
655 use_smbus == I2C_SMBUS_BYTE_DATA) {
656 dev_notice(&client->dev, "Falling back to %s reads, "
657 "performance will suffer\n", use_smbus ==
658 I2C_SMBUS_WORD_DATA ? "word" : "byte");
661 /* export data to kernel code */
663 chip.setup(at24->nvmem, chip.context);
668 for (i = 1; i < num_addresses; i++)
670 i2c_unregister_device(at24->client[i]);
675 static int at24_remove(struct i2c_client *client)
677 struct at24_data *at24;
680 at24 = i2c_get_clientdata(client);
682 nvmem_unregister(at24->nvmem);
684 for (i = 1; i < at24->num_addresses; i++)
685 i2c_unregister_device(at24->client[i]);
690 /*-------------------------------------------------------------------------*/
692 static struct i2c_driver at24_driver = {
695 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
698 .remove = at24_remove,
699 .id_table = at24_ids,
702 static int __init at24_init(void)
705 pr_err("at24: io_limit must not be 0!\n");
709 io_limit = rounddown_pow_of_two(io_limit);
710 return i2c_add_driver(&at24_driver);
712 module_init(at24_init);
714 static void __exit at24_exit(void)
716 i2c_del_driver(&at24_driver);
718 module_exit(at24_exit);
720 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
721 MODULE_AUTHOR("David Brownell and Wolfram Sang");
722 MODULE_LICENSE("GPL");