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 addrbuf[0] = 0x90 + offset;
370 msg[1].addr = client->addr;
371 msg[1].flags = I2C_M_RD;
375 loop_until_timeout(timeout, read_time) {
376 status = i2c_transfer(client->adapter, msg, 2);
385 * Note that if the hardware write-protect pin is pulled high, the whole
386 * chip is normally write protected. But there are plenty of product
387 * variants here, including OTP fuses and partial chip protect.
389 * We only use page mode writes; the alternative is sloooow. These routines
390 * write at most one page.
393 static size_t at24_adjust_write_count(struct at24_data *at24,
394 unsigned int offset, size_t count)
398 /* write_max is at most a page */
399 if (count > at24->write_max)
400 count = at24->write_max;
402 /* Never roll over backwards, to the start of this page */
403 next_page = roundup(offset + 1, at24->chip.page_size);
404 if (offset + count > next_page)
405 count = next_page - offset;
410 static ssize_t at24_eeprom_write_smbus_block(struct at24_data *at24,
412 unsigned int offset, size_t count)
414 unsigned long timeout, write_time;
415 struct i2c_client *client;
418 client = at24_translate_offset(at24, &offset);
419 count = at24_adjust_write_count(at24, offset, count);
421 loop_until_timeout(timeout, write_time) {
422 status = i2c_smbus_write_i2c_block_data(client,
427 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
428 count, offset, status, jiffies);
437 static ssize_t at24_eeprom_write_smbus_byte(struct at24_data *at24,
439 unsigned int offset, size_t count)
441 unsigned long timeout, write_time;
442 struct i2c_client *client;
445 client = at24_translate_offset(at24, &offset);
447 loop_until_timeout(timeout, write_time) {
448 status = i2c_smbus_write_byte_data(client, offset, buf[0]);
452 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
453 count, offset, status, jiffies);
462 static ssize_t at24_eeprom_write_i2c(struct at24_data *at24, const char *buf,
463 unsigned int offset, size_t count)
465 unsigned long timeout, write_time;
466 struct i2c_client *client;
471 client = at24_translate_offset(at24, &offset);
472 count = at24_adjust_write_count(at24, offset, count);
474 msg.addr = client->addr;
477 /* msg.buf is u8 and casts will mask the values */
478 msg.buf = at24->writebuf;
479 if (at24->chip.flags & AT24_FLAG_ADDR16)
480 msg.buf[i++] = offset >> 8;
482 msg.buf[i++] = offset;
483 memcpy(&msg.buf[i], buf, count);
486 loop_until_timeout(timeout, write_time) {
487 status = i2c_transfer(client->adapter, &msg, 1);
491 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
492 count, offset, status, jiffies);
501 static int at24_read(void *priv, unsigned int off, void *val, size_t count)
503 struct at24_data *at24 = priv;
506 if (unlikely(!count))
510 * Read data from chip, protecting against concurrent updates
511 * from this host, but not from other I2C masters.
513 mutex_lock(&at24->lock);
518 status = at24->read_func(at24, buf, off, count);
520 mutex_unlock(&at24->lock);
528 mutex_unlock(&at24->lock);
533 static int at24_write(void *priv, unsigned int off, void *val, size_t count)
535 struct at24_data *at24 = priv;
538 if (unlikely(!count))
542 * Write data to chip, protecting against concurrent updates
543 * from this host, but not from other I2C masters.
545 mutex_lock(&at24->lock);
550 status = at24->write_func(at24, buf, off, count);
552 mutex_unlock(&at24->lock);
560 mutex_unlock(&at24->lock);
565 static void at24_get_pdata(struct device *dev, struct at24_platform_data *chip)
570 if (device_property_present(dev, "read-only"))
571 chip->flags |= AT24_FLAG_READONLY;
573 err = device_property_read_u32(dev, "pagesize", &val);
575 chip->page_size = val;
578 * This is slow, but we can't know all eeproms, so we better
579 * play safe. Specifying custom eeprom-types via platform_data
580 * is recommended anyhow.
586 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
588 struct at24_platform_data chip;
589 kernel_ulong_t magic = 0;
592 int use_smbus_write = 0;
593 struct at24_data *at24;
595 unsigned i, num_addresses;
598 if (client->dev.platform_data) {
599 chip = *(struct at24_platform_data *)client->dev.platform_data;
602 magic = id->driver_data;
604 const struct acpi_device_id *aid;
606 aid = acpi_match_device(at24_acpi_ids, &client->dev);
608 magic = aid->driver_data;
613 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
614 magic >>= AT24_SIZE_BYTELEN;
615 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
617 at24_get_pdata(&client->dev, &chip);
623 if (!is_power_of_2(chip.byte_len))
624 dev_warn(&client->dev,
625 "byte_len looks suspicious (no power of 2)!\n");
626 if (!chip.page_size) {
627 dev_err(&client->dev, "page_size must not be 0!\n");
630 if (!is_power_of_2(chip.page_size))
631 dev_warn(&client->dev,
632 "page_size looks suspicious (no power of 2)!\n");
634 /* Use I2C operations unless we're stuck with SMBus extensions. */
635 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
636 if (chip.flags & AT24_FLAG_ADDR16)
637 return -EPFNOSUPPORT;
639 if (i2c_check_functionality(client->adapter,
640 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
641 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
642 } else if (i2c_check_functionality(client->adapter,
643 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
644 use_smbus = I2C_SMBUS_WORD_DATA;
645 } else if (i2c_check_functionality(client->adapter,
646 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
647 use_smbus = I2C_SMBUS_BYTE_DATA;
649 return -EPFNOSUPPORT;
652 if (i2c_check_functionality(client->adapter,
653 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
654 use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
655 } else if (i2c_check_functionality(client->adapter,
656 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
657 use_smbus_write = I2C_SMBUS_BYTE_DATA;
662 if (chip.flags & AT24_FLAG_TAKE8ADDR)
665 num_addresses = DIV_ROUND_UP(chip.byte_len,
666 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
668 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
669 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
673 mutex_init(&at24->lock);
674 at24->use_smbus = use_smbus;
675 at24->use_smbus_write = use_smbus_write;
677 at24->num_addresses = num_addresses;
679 if ((chip.flags & AT24_FLAG_SERIAL) && (chip.flags & AT24_FLAG_MAC)) {
680 dev_err(&client->dev,
681 "invalid device data - cannot have both AT24_FLAG_SERIAL & AT24_FLAG_MAC.");
685 if (chip.flags & AT24_FLAG_SERIAL) {
686 at24->read_func = at24_eeprom_read_serial;
687 } else if (chip.flags & AT24_FLAG_MAC) {
688 at24->read_func = at24_eeprom_read_mac;
690 at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
691 : at24_eeprom_read_i2c;
694 if (at24->use_smbus) {
695 if (at24->use_smbus_write == I2C_SMBUS_I2C_BLOCK_DATA)
696 at24->write_func = at24_eeprom_write_smbus_block;
698 at24->write_func = at24_eeprom_write_smbus_byte;
700 at24->write_func = at24_eeprom_write_i2c;
703 writable = !(chip.flags & AT24_FLAG_READONLY);
705 if (!use_smbus || use_smbus_write) {
707 unsigned write_max = chip.page_size;
709 if (write_max > io_limit)
710 write_max = io_limit;
711 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
712 write_max = I2C_SMBUS_BLOCK_MAX;
713 at24->write_max = write_max;
715 /* buffer (data + address at the beginning) */
716 at24->writebuf = devm_kzalloc(&client->dev,
717 write_max + 2, GFP_KERNEL);
721 dev_warn(&client->dev,
722 "cannot write due to controller restrictions.");
726 at24->client[0] = client;
728 /* use dummy devices for multiple-address chips */
729 for (i = 1; i < num_addresses; i++) {
730 at24->client[i] = i2c_new_dummy(client->adapter,
732 if (!at24->client[i]) {
733 dev_err(&client->dev, "address 0x%02x unavailable\n",
740 i2c_set_clientdata(client, at24);
743 * Perform a one-byte test read to verify that the
744 * chip is functional.
746 err = at24_read(at24, 0, &test_byte, 1);
752 at24->nvmem_config.name = dev_name(&client->dev);
753 at24->nvmem_config.dev = &client->dev;
754 at24->nvmem_config.read_only = !writable;
755 at24->nvmem_config.root_only = true;
756 at24->nvmem_config.owner = THIS_MODULE;
757 at24->nvmem_config.compat = true;
758 at24->nvmem_config.base_dev = &client->dev;
759 at24->nvmem_config.reg_read = at24_read;
760 at24->nvmem_config.reg_write = at24_write;
761 at24->nvmem_config.priv = at24;
762 at24->nvmem_config.stride = 4;
763 at24->nvmem_config.word_size = 1;
764 at24->nvmem_config.size = chip.byte_len;
766 at24->nvmem = nvmem_register(&at24->nvmem_config);
768 if (IS_ERR(at24->nvmem)) {
769 err = PTR_ERR(at24->nvmem);
773 dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
774 chip.byte_len, client->name,
775 writable ? "writable" : "read-only", at24->write_max);
776 if (use_smbus == I2C_SMBUS_WORD_DATA ||
777 use_smbus == I2C_SMBUS_BYTE_DATA) {
778 dev_notice(&client->dev, "Falling back to %s reads, "
779 "performance will suffer\n", use_smbus ==
780 I2C_SMBUS_WORD_DATA ? "word" : "byte");
783 /* export data to kernel code */
785 chip.setup(at24->nvmem, chip.context);
790 for (i = 1; i < num_addresses; i++)
792 i2c_unregister_device(at24->client[i]);
797 static int at24_remove(struct i2c_client *client)
799 struct at24_data *at24;
802 at24 = i2c_get_clientdata(client);
804 nvmem_unregister(at24->nvmem);
806 for (i = 1; i < at24->num_addresses; i++)
807 i2c_unregister_device(at24->client[i]);
812 /*-------------------------------------------------------------------------*/
814 static struct i2c_driver at24_driver = {
817 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
820 .remove = at24_remove,
821 .id_table = at24_ids,
824 static int __init at24_init(void)
827 pr_err("at24: io_limit must not be 0!\n");
831 io_limit = rounddown_pow_of_two(io_limit);
832 return i2c_add_driver(&at24_driver);
834 module_init(at24_init);
836 static void __exit at24_exit(void)
838 i2c_del_driver(&at24_driver);
840 module_exit(at24_exit);
842 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
843 MODULE_AUTHOR("David Brownell and Wolfram Sang");
844 MODULE_LICENSE("GPL");