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>
22 #include <linux/property.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
119 * write to work while making sure that at least one iteration is run before
120 * checking the break condition.
122 * It takes two parameters: a variable in which the future timeout in jiffies
123 * will be stored and a temporary variable holding the time of the last
124 * iteration of processing the request. Both should be unsigned integers
125 * holding at least 32 bits.
127 #define loop_until_timeout(tout, op_time) \
128 for (tout = jiffies + msecs_to_jiffies(write_timeout), op_time = 0; \
129 op_time ? time_before(op_time, tout) : true; \
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 { "24cs01", AT24_DEVICE_MAGIC(16,
138 AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
139 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
140 { "24cs02", AT24_DEVICE_MAGIC(16,
141 AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
142 { "24mac402", AT24_DEVICE_MAGIC(48 / 8,
143 AT24_FLAG_MAC | AT24_FLAG_READONLY) },
144 { "24mac602", AT24_DEVICE_MAGIC(64 / 8,
145 AT24_FLAG_MAC | AT24_FLAG_READONLY) },
146 /* spd is a 24c02 in memory DIMMs */
147 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
148 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
149 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
150 { "24cs04", AT24_DEVICE_MAGIC(16,
151 AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
152 /* 24rf08 quirk is handled at i2c-core */
153 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
154 { "24cs08", AT24_DEVICE_MAGIC(16,
155 AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
156 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
157 { "24cs16", AT24_DEVICE_MAGIC(16,
158 AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
159 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
160 { "24cs32", AT24_DEVICE_MAGIC(16,
163 AT24_FLAG_READONLY) },
164 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
165 { "24cs64", AT24_DEVICE_MAGIC(16,
168 AT24_FLAG_READONLY) },
169 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
170 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
171 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
172 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
174 { /* END OF LIST */ }
176 MODULE_DEVICE_TABLE(i2c, at24_ids);
178 static const struct acpi_device_id at24_acpi_ids[] = {
179 { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
182 MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
184 /*-------------------------------------------------------------------------*/
187 * This routine supports chips which consume multiple I2C addresses. It
188 * computes the addressing information to be used for a given r/w request.
189 * Assumes that sanity checks for offset happened at sysfs-layer.
191 * Slave address and byte offset derive from the offset. Always
192 * set the byte address; on a multi-master board, another master
193 * may have changed the chip's "current" address pointer.
195 * REVISIT some multi-address chips don't rollover page reads to
196 * the next slave address, so we may need to truncate the count.
197 * Those chips might need another quirk flag.
199 * If the real hardware used four adjacent 24c02 chips and that
200 * were misconfigured as one 24c08, that would be a similar effect:
201 * one "eeprom" file not four, but larger reads would fail when
202 * they crossed certain pages.
204 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
205 unsigned int *offset)
209 if (at24->chip.flags & AT24_FLAG_ADDR16) {
217 return at24->client[i];
220 static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf,
221 unsigned int offset, size_t count)
223 unsigned long timeout, read_time;
224 struct i2c_client *client;
227 client = at24_translate_offset(at24, &offset);
229 if (count > io_limit)
232 /* Smaller eeproms can work given some SMBus extension calls */
233 if (count > I2C_SMBUS_BLOCK_MAX)
234 count = I2C_SMBUS_BLOCK_MAX;
236 loop_until_timeout(timeout, read_time) {
237 status = i2c_smbus_read_i2c_block_data_or_emulated(client,
241 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
242 count, offset, status, jiffies);
251 static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
252 unsigned int offset, size_t count)
254 unsigned long timeout, read_time;
255 struct i2c_client *client;
256 struct i2c_msg msg[2];
260 memset(msg, 0, sizeof(msg));
261 client = at24_translate_offset(at24, &offset);
263 if (count > io_limit)
267 * When we have a better choice than SMBus calls, use a combined I2C
268 * message. Write address; then read up to io_limit data bytes. Note
269 * that read page rollover helps us here (unlike writes). msgbuf is
270 * u8 and will cast to our needs.
273 if (at24->chip.flags & AT24_FLAG_ADDR16)
274 msgbuf[i++] = offset >> 8;
275 msgbuf[i++] = offset;
277 msg[0].addr = client->addr;
281 msg[1].addr = client->addr;
282 msg[1].flags = I2C_M_RD;
286 loop_until_timeout(timeout, read_time) {
287 status = i2c_transfer(client->adapter, msg, 2);
291 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
292 count, offset, status, jiffies);
301 static ssize_t at24_eeprom_read_serial(struct at24_data *at24, char *buf,
302 unsigned int offset, size_t count)
304 unsigned long timeout, read_time;
305 struct i2c_client *client;
306 struct i2c_msg msg[2];
310 client = at24_translate_offset(at24, &offset);
312 memset(msg, 0, sizeof(msg));
313 msg[0].addr = client->addr;
314 msg[0].buf = addrbuf;
317 * The address pointer of the device is shared between the regular
318 * EEPROM array and the serial number block. The dummy write (part of
319 * the sequential read protocol) ensures the address pointer is reset
320 * to the desired position.
322 if (at24->chip.flags & AT24_FLAG_ADDR16) {
324 * For 16 bit address pointers, the word address must contain
325 * a '10' sequence in bits 11 and 10 regardless of the
326 * intended position of the address pointer.
333 * Otherwise the word address must begin with a '10' sequence,
334 * regardless of the intended address.
336 addrbuf[0] = 0x80 + offset;
340 msg[1].addr = client->addr;
341 msg[1].flags = I2C_M_RD;
345 loop_until_timeout(timeout, read_time) {
346 status = i2c_transfer(client->adapter, msg, 2);
354 static ssize_t at24_eeprom_read_mac(struct at24_data *at24, char *buf,
355 unsigned int offset, size_t count)
357 unsigned long timeout, read_time;
358 struct i2c_client *client;
359 struct i2c_msg msg[2];
363 client = at24_translate_offset(at24, &offset);
365 memset(msg, 0, sizeof(msg));
366 msg[0].addr = client->addr;
367 msg[0].buf = addrbuf;
368 /* EUI-48 starts from 0x9a, EUI-64 from 0x98 */
369 addrbuf[0] = 0xa0 - at24->chip.byte_len + offset;
371 msg[1].addr = client->addr;
372 msg[1].flags = I2C_M_RD;
376 loop_until_timeout(timeout, read_time) {
377 status = i2c_transfer(client->adapter, msg, 2);
386 * Note that if the hardware write-protect pin is pulled high, the whole
387 * chip is normally write protected. But there are plenty of product
388 * variants here, including OTP fuses and partial chip protect.
390 * We only use page mode writes; the alternative is sloooow. These routines
391 * write at most one page.
394 static size_t at24_adjust_write_count(struct at24_data *at24,
395 unsigned int offset, size_t count)
399 /* write_max is at most a page */
400 if (count > at24->write_max)
401 count = at24->write_max;
403 /* Never roll over backwards, to the start of this page */
404 next_page = roundup(offset + 1, at24->chip.page_size);
405 if (offset + count > next_page)
406 count = next_page - offset;
411 static ssize_t at24_eeprom_write_smbus_block(struct at24_data *at24,
413 unsigned int offset, size_t count)
415 unsigned long timeout, write_time;
416 struct i2c_client *client;
419 client = at24_translate_offset(at24, &offset);
420 count = at24_adjust_write_count(at24, offset, count);
422 loop_until_timeout(timeout, write_time) {
423 status = i2c_smbus_write_i2c_block_data(client,
428 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
429 count, offset, status, jiffies);
438 static ssize_t at24_eeprom_write_smbus_byte(struct at24_data *at24,
440 unsigned int offset, size_t count)
442 unsigned long timeout, write_time;
443 struct i2c_client *client;
446 client = at24_translate_offset(at24, &offset);
448 loop_until_timeout(timeout, write_time) {
449 status = i2c_smbus_write_byte_data(client, offset, buf[0]);
453 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
454 count, offset, status, jiffies);
463 static ssize_t at24_eeprom_write_i2c(struct at24_data *at24, const char *buf,
464 unsigned int offset, size_t count)
466 unsigned long timeout, write_time;
467 struct i2c_client *client;
472 client = at24_translate_offset(at24, &offset);
473 count = at24_adjust_write_count(at24, offset, count);
475 msg.addr = client->addr;
478 /* msg.buf is u8 and casts will mask the values */
479 msg.buf = at24->writebuf;
480 if (at24->chip.flags & AT24_FLAG_ADDR16)
481 msg.buf[i++] = offset >> 8;
483 msg.buf[i++] = offset;
484 memcpy(&msg.buf[i], buf, count);
487 loop_until_timeout(timeout, write_time) {
488 status = i2c_transfer(client->adapter, &msg, 1);
492 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
493 count, offset, status, jiffies);
502 static int at24_read(void *priv, unsigned int off, void *val, size_t count)
504 struct at24_data *at24 = priv;
507 if (unlikely(!count))
511 * Read data from chip, protecting against concurrent updates
512 * from this host, but not from other I2C masters.
514 mutex_lock(&at24->lock);
519 status = at24->read_func(at24, buf, off, count);
521 mutex_unlock(&at24->lock);
529 mutex_unlock(&at24->lock);
534 static int at24_write(void *priv, unsigned int off, void *val, size_t count)
536 struct at24_data *at24 = priv;
539 if (unlikely(!count))
543 * Write data to chip, protecting against concurrent updates
544 * from this host, but not from other I2C masters.
546 mutex_lock(&at24->lock);
551 status = at24->write_func(at24, buf, off, count);
553 mutex_unlock(&at24->lock);
561 mutex_unlock(&at24->lock);
566 static void at24_get_pdata(struct device *dev, struct at24_platform_data *chip)
571 if (device_property_present(dev, "read-only"))
572 chip->flags |= AT24_FLAG_READONLY;
574 err = device_property_read_u32(dev, "pagesize", &val);
576 chip->page_size = val;
579 * This is slow, but we can't know all eeproms, so we better
580 * play safe. Specifying custom eeprom-types via platform_data
581 * is recommended anyhow.
587 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
589 struct at24_platform_data chip;
590 kernel_ulong_t magic = 0;
593 int use_smbus_write = 0;
594 struct at24_data *at24;
596 unsigned i, num_addresses;
599 if (client->dev.platform_data) {
600 chip = *(struct at24_platform_data *)client->dev.platform_data;
603 magic = id->driver_data;
605 const struct acpi_device_id *aid;
607 aid = acpi_match_device(at24_acpi_ids, &client->dev);
609 magic = aid->driver_data;
614 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
615 magic >>= AT24_SIZE_BYTELEN;
616 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
618 at24_get_pdata(&client->dev, &chip);
624 if (!is_power_of_2(chip.byte_len))
625 dev_warn(&client->dev,
626 "byte_len looks suspicious (no power of 2)!\n");
627 if (!chip.page_size) {
628 dev_err(&client->dev, "page_size must not be 0!\n");
631 if (!is_power_of_2(chip.page_size))
632 dev_warn(&client->dev,
633 "page_size looks suspicious (no power of 2)!\n");
635 /* Use I2C operations unless we're stuck with SMBus extensions. */
636 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
637 if (chip.flags & AT24_FLAG_ADDR16)
638 return -EPFNOSUPPORT;
640 if (i2c_check_functionality(client->adapter,
641 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
642 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
643 } else if (i2c_check_functionality(client->adapter,
644 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
645 use_smbus = I2C_SMBUS_WORD_DATA;
646 } else if (i2c_check_functionality(client->adapter,
647 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
648 use_smbus = I2C_SMBUS_BYTE_DATA;
650 return -EPFNOSUPPORT;
653 if (i2c_check_functionality(client->adapter,
654 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
655 use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
656 } else if (i2c_check_functionality(client->adapter,
657 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
658 use_smbus_write = I2C_SMBUS_BYTE_DATA;
663 if (chip.flags & AT24_FLAG_TAKE8ADDR)
666 num_addresses = DIV_ROUND_UP(chip.byte_len,
667 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
669 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
670 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
674 mutex_init(&at24->lock);
675 at24->use_smbus = use_smbus;
676 at24->use_smbus_write = use_smbus_write;
678 at24->num_addresses = num_addresses;
680 if ((chip.flags & AT24_FLAG_SERIAL) && (chip.flags & AT24_FLAG_MAC)) {
681 dev_err(&client->dev,
682 "invalid device data - cannot have both AT24_FLAG_SERIAL & AT24_FLAG_MAC.");
686 if (chip.flags & AT24_FLAG_SERIAL) {
687 at24->read_func = at24_eeprom_read_serial;
688 } else if (chip.flags & AT24_FLAG_MAC) {
689 at24->read_func = at24_eeprom_read_mac;
691 at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
692 : at24_eeprom_read_i2c;
695 if (at24->use_smbus) {
696 if (at24->use_smbus_write == I2C_SMBUS_I2C_BLOCK_DATA)
697 at24->write_func = at24_eeprom_write_smbus_block;
699 at24->write_func = at24_eeprom_write_smbus_byte;
701 at24->write_func = at24_eeprom_write_i2c;
704 writable = !(chip.flags & AT24_FLAG_READONLY);
706 if (!use_smbus || use_smbus_write) {
708 unsigned write_max = chip.page_size;
710 if (write_max > io_limit)
711 write_max = io_limit;
712 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
713 write_max = I2C_SMBUS_BLOCK_MAX;
714 at24->write_max = write_max;
716 /* buffer (data + address at the beginning) */
717 at24->writebuf = devm_kzalloc(&client->dev,
718 write_max + 2, GFP_KERNEL);
722 dev_warn(&client->dev,
723 "cannot write due to controller restrictions.");
727 at24->client[0] = client;
729 /* use dummy devices for multiple-address chips */
730 for (i = 1; i < num_addresses; i++) {
731 at24->client[i] = i2c_new_dummy(client->adapter,
733 if (!at24->client[i]) {
734 dev_err(&client->dev, "address 0x%02x unavailable\n",
741 i2c_set_clientdata(client, at24);
744 * Perform a one-byte test read to verify that the
745 * chip is functional.
747 err = at24_read(at24, 0, &test_byte, 1);
753 at24->nvmem_config.name = dev_name(&client->dev);
754 at24->nvmem_config.dev = &client->dev;
755 at24->nvmem_config.read_only = !writable;
756 at24->nvmem_config.root_only = true;
757 at24->nvmem_config.owner = THIS_MODULE;
758 at24->nvmem_config.compat = true;
759 at24->nvmem_config.base_dev = &client->dev;
760 at24->nvmem_config.reg_read = at24_read;
761 at24->nvmem_config.reg_write = at24_write;
762 at24->nvmem_config.priv = at24;
763 at24->nvmem_config.stride = 4;
764 at24->nvmem_config.word_size = 1;
765 at24->nvmem_config.size = chip.byte_len;
767 at24->nvmem = nvmem_register(&at24->nvmem_config);
769 if (IS_ERR(at24->nvmem)) {
770 err = PTR_ERR(at24->nvmem);
774 dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
775 chip.byte_len, client->name,
776 writable ? "writable" : "read-only", at24->write_max);
777 if (use_smbus == I2C_SMBUS_WORD_DATA ||
778 use_smbus == I2C_SMBUS_BYTE_DATA) {
779 dev_notice(&client->dev, "Falling back to %s reads, "
780 "performance will suffer\n", use_smbus ==
781 I2C_SMBUS_WORD_DATA ? "word" : "byte");
784 /* export data to kernel code */
786 chip.setup(at24->nvmem, chip.context);
791 for (i = 1; i < num_addresses; i++)
793 i2c_unregister_device(at24->client[i]);
798 static int at24_remove(struct i2c_client *client)
800 struct at24_data *at24;
803 at24 = i2c_get_clientdata(client);
805 nvmem_unregister(at24->nvmem);
807 for (i = 1; i < at24->num_addresses; i++)
808 i2c_unregister_device(at24->client[i]);
813 /*-------------------------------------------------------------------------*/
815 static struct i2c_driver at24_driver = {
818 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
821 .remove = at24_remove,
822 .id_table = at24_ids,
825 static int __init at24_init(void)
828 pr_err("at24: io_limit must not be 0!\n");
832 io_limit = rounddown_pow_of_two(io_limit);
833 return i2c_add_driver(&at24_driver);
835 module_init(at24_init);
837 static void __exit at24_exit(void)
839 i2c_del_driver(&at24_driver);
841 module_exit(at24_exit);
843 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
844 MODULE_AUTHOR("David Brownell and Wolfram Sang");
845 MODULE_LICENSE("GPL");