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
;
62 * Lock protects against activities from other Linux tasks,
63 * but not from changes by other I2C masters.
66 struct bin_attribute bin
;
70 unsigned num_addresses
;
73 * Some chips tie up multiple I2C addresses; dummy devices reserve
74 * them for us, and we'll use them with SMBus calls.
76 struct i2c_client
*client
[];
80 * This parameter is to help this driver avoid blocking other drivers out
81 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
82 * clock, one 256 byte read takes about 1/43 second which is excessive;
83 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
84 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
86 * This value is forced to be a power of two so that writes align on pages.
88 static unsigned io_limit
= 128;
89 module_param(io_limit
, uint
, 0);
90 MODULE_PARM_DESC(io_limit
, "Maximum bytes per I/O (default 128)");
93 * Specs often allow 5 msec for a page write, sometimes 20 msec;
94 * it's important to recover from write timeouts.
96 static unsigned write_timeout
= 25;
97 module_param(write_timeout
, uint
, 0);
98 MODULE_PARM_DESC(write_timeout
, "Time (in ms) to try writes (default 25)");
100 #define AT24_SIZE_BYTELEN 5
101 #define AT24_SIZE_FLAGS 8
103 #define AT24_BITMASK(x) (BIT(x) - 1)
105 /* create non-zero magic value for given eeprom parameters */
106 #define AT24_DEVICE_MAGIC(_len, _flags) \
107 ((1 << AT24_SIZE_FLAGS | (_flags)) \
108 << AT24_SIZE_BYTELEN | ilog2(_len))
110 static const struct i2c_device_id at24_ids
[] = {
111 /* needs 8 addresses as A0-A2 are ignored */
112 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR
) },
113 /* old variants can't be handled with this generic entry! */
114 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
115 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
116 /* spd is a 24c02 in memory DIMMs */
117 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
118 AT24_FLAG_READONLY
| AT24_FLAG_IRUGO
) },
119 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
120 /* 24rf08 quirk is handled at i2c-core */
121 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
122 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
123 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16
) },
124 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16
) },
125 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16
) },
126 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16
) },
127 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16
) },
128 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16
) },
130 { /* END OF LIST */ }
132 MODULE_DEVICE_TABLE(i2c
, at24_ids
);
134 /*-------------------------------------------------------------------------*/
137 * This routine supports chips which consume multiple I2C addresses. It
138 * computes the addressing information to be used for a given r/w request.
139 * Assumes that sanity checks for offset happened at sysfs-layer.
141 static struct i2c_client
*at24_translate_offset(struct at24_data
*at24
,
146 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
) {
154 return at24
->client
[i
];
157 static ssize_t
at24_eeprom_read(struct at24_data
*at24
, char *buf
,
158 unsigned offset
, size_t count
)
160 struct i2c_msg msg
[2];
162 struct i2c_client
*client
;
163 unsigned long timeout
, read_time
;
166 memset(msg
, 0, sizeof(msg
));
169 * REVISIT some multi-address chips don't rollover page reads to
170 * the next slave address, so we may need to truncate the count.
171 * Those chips might need another quirk flag.
173 * If the real hardware used four adjacent 24c02 chips and that
174 * were misconfigured as one 24c08, that would be a similar effect:
175 * one "eeprom" file not four, but larger reads would fail when
176 * they crossed certain pages.
180 * Slave address and byte offset derive from the offset. Always
181 * set the byte address; on a multi-master board, another master
182 * may have changed the chip's "current" address pointer.
184 client
= at24_translate_offset(at24
, &offset
);
186 if (count
> io_limit
)
189 if (at24
->use_smbus
) {
190 /* Smaller eeproms can work given some SMBus extension calls */
191 if (count
> I2C_SMBUS_BLOCK_MAX
)
192 count
= I2C_SMBUS_BLOCK_MAX
;
195 * When we have a better choice than SMBus calls, use a
196 * combined I2C message. Write address; then read up to
197 * io_limit data bytes. Note that read page rollover helps us
198 * here (unlike writes). msgbuf is u8 and will cast to our
202 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
)
203 msgbuf
[i
++] = offset
>> 8;
204 msgbuf
[i
++] = offset
;
206 msg
[0].addr
= client
->addr
;
210 msg
[1].addr
= client
->addr
;
211 msg
[1].flags
= I2C_M_RD
;
217 * Reads fail if the previous write didn't complete yet. We may
218 * loop a few times until this one succeeds, waiting at least
219 * long enough for one entire page write to work.
221 timeout
= jiffies
+ msecs_to_jiffies(write_timeout
);
224 if (at24
->use_smbus
) {
225 status
= i2c_smbus_read_i2c_block_data_or_emulated(client
, offset
,
228 status
= i2c_transfer(client
->adapter
, msg
, 2);
232 dev_dbg(&client
->dev
, "read %zu@%d --> %d (%ld)\n",
233 count
, offset
, status
, jiffies
);
238 /* REVISIT: at HZ=100, this is sloooow */
240 } while (time_before(read_time
, timeout
));
245 static ssize_t
at24_read(struct at24_data
*at24
,
246 char *buf
, loff_t off
, size_t count
)
250 if (unlikely(!count
))
254 * Read data from chip, protecting against concurrent updates
255 * from this host, but not from other I2C masters.
257 mutex_lock(&at24
->lock
);
262 status
= at24_eeprom_read(at24
, buf
, off
, count
);
274 mutex_unlock(&at24
->lock
);
279 static ssize_t
at24_bin_read(struct file
*filp
, struct kobject
*kobj
,
280 struct bin_attribute
*attr
,
281 char *buf
, loff_t off
, size_t count
)
283 struct at24_data
*at24
;
285 at24
= dev_get_drvdata(container_of(kobj
, struct device
, kobj
));
286 return at24_read(at24
, buf
, off
, count
);
291 * Note that if the hardware write-protect pin is pulled high, the whole
292 * chip is normally write protected. But there are plenty of product
293 * variants here, including OTP fuses and partial chip protect.
295 * We only use page mode writes; the alternative is sloooow. This routine
296 * writes at most one page.
298 static ssize_t
at24_eeprom_write(struct at24_data
*at24
, const char *buf
,
299 unsigned offset
, size_t count
)
301 struct i2c_client
*client
;
304 unsigned long timeout
, write_time
;
307 /* Get corresponding I2C address and adjust offset */
308 client
= at24_translate_offset(at24
, &offset
);
310 /* write_max is at most a page */
311 if (count
> at24
->write_max
)
312 count
= at24
->write_max
;
314 /* Never roll over backwards, to the start of this page */
315 next_page
= roundup(offset
+ 1, at24
->chip
.page_size
);
316 if (offset
+ count
> next_page
)
317 count
= next_page
- offset
;
319 /* If we'll use I2C calls for I/O, set up the message */
320 if (!at24
->use_smbus
) {
323 msg
.addr
= client
->addr
;
326 /* msg.buf is u8 and casts will mask the values */
327 msg
.buf
= at24
->writebuf
;
328 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
)
329 msg
.buf
[i
++] = offset
>> 8;
331 msg
.buf
[i
++] = offset
;
332 memcpy(&msg
.buf
[i
], buf
, count
);
337 * Writes fail if the previous one didn't complete yet. We may
338 * loop a few times until this one succeeds, waiting at least
339 * long enough for one entire page write to work.
341 timeout
= jiffies
+ msecs_to_jiffies(write_timeout
);
343 write_time
= jiffies
;
344 if (at24
->use_smbus_write
) {
345 switch (at24
->use_smbus_write
) {
346 case I2C_SMBUS_I2C_BLOCK_DATA
:
347 status
= i2c_smbus_write_i2c_block_data(client
,
350 case I2C_SMBUS_BYTE_DATA
:
351 status
= i2c_smbus_write_byte_data(client
,
359 status
= i2c_transfer(client
->adapter
, &msg
, 1);
363 dev_dbg(&client
->dev
, "write %zu@%d --> %zd (%ld)\n",
364 count
, offset
, status
, jiffies
);
369 /* REVISIT: at HZ=100, this is sloooow */
371 } while (time_before(write_time
, timeout
));
376 static ssize_t
at24_write(struct at24_data
*at24
, const char *buf
, loff_t off
,
381 if (unlikely(!count
))
385 * Write data to chip, protecting against concurrent updates
386 * from this host, but not from other I2C masters.
388 mutex_lock(&at24
->lock
);
393 status
= at24_eeprom_write(at24
, buf
, off
, count
);
405 mutex_unlock(&at24
->lock
);
410 static ssize_t
at24_bin_write(struct file
*filp
, struct kobject
*kobj
,
411 struct bin_attribute
*attr
,
412 char *buf
, loff_t off
, size_t count
)
414 struct at24_data
*at24
;
416 at24
= dev_get_drvdata(container_of(kobj
, struct device
, kobj
));
417 return at24_write(at24
, buf
, off
, count
);
420 /*-------------------------------------------------------------------------*/
423 * This lets other kernel code access the eeprom data. For example, it
424 * might hold a board's Ethernet address, or board-specific calibration
425 * data generated on the manufacturing floor.
428 static ssize_t
at24_macc_read(struct memory_accessor
*macc
, char *buf
,
429 off_t offset
, size_t count
)
431 struct at24_data
*at24
= container_of(macc
, struct at24_data
, macc
);
433 return at24_read(at24
, buf
, offset
, count
);
436 static ssize_t
at24_macc_write(struct memory_accessor
*macc
, const char *buf
,
437 off_t offset
, size_t count
)
439 struct at24_data
*at24
= container_of(macc
, struct at24_data
, macc
);
441 return at24_write(at24
, buf
, offset
, count
);
444 /*-------------------------------------------------------------------------*/
447 static void at24_get_ofdata(struct i2c_client
*client
,
448 struct at24_platform_data
*chip
)
451 struct device_node
*node
= client
->dev
.of_node
;
454 if (of_get_property(node
, "read-only", NULL
))
455 chip
->flags
|= AT24_FLAG_READONLY
;
456 val
= of_get_property(node
, "pagesize", NULL
);
458 chip
->page_size
= be32_to_cpup(val
);
462 static void at24_get_ofdata(struct i2c_client
*client
,
463 struct at24_platform_data
*chip
)
465 #endif /* CONFIG_OF */
467 static int at24_probe(struct i2c_client
*client
, const struct i2c_device_id
*id
)
469 struct at24_platform_data chip
;
472 int use_smbus_write
= 0;
473 struct at24_data
*at24
;
475 unsigned i
, num_addresses
;
476 kernel_ulong_t magic
;
478 if (client
->dev
.platform_data
) {
479 chip
= *(struct at24_platform_data
*)client
->dev
.platform_data
;
481 if (!id
->driver_data
)
484 magic
= id
->driver_data
;
485 chip
.byte_len
= BIT(magic
& AT24_BITMASK(AT24_SIZE_BYTELEN
));
486 magic
>>= AT24_SIZE_BYTELEN
;
487 chip
.flags
= magic
& AT24_BITMASK(AT24_SIZE_FLAGS
);
489 * This is slow, but we can't know all eeproms, so we better
490 * play safe. Specifying custom eeprom-types via platform_data
491 * is recommended anyhow.
495 /* update chipdata if OF is present */
496 at24_get_ofdata(client
, &chip
);
502 if (!is_power_of_2(chip
.byte_len
))
503 dev_warn(&client
->dev
,
504 "byte_len looks suspicious (no power of 2)!\n");
505 if (!chip
.page_size
) {
506 dev_err(&client
->dev
, "page_size must not be 0!\n");
509 if (!is_power_of_2(chip
.page_size
))
510 dev_warn(&client
->dev
,
511 "page_size looks suspicious (no power of 2)!\n");
513 /* Use I2C operations unless we're stuck with SMBus extensions. */
514 if (!i2c_check_functionality(client
->adapter
, I2C_FUNC_I2C
)) {
515 if (chip
.flags
& AT24_FLAG_ADDR16
)
516 return -EPFNOSUPPORT
;
518 if (i2c_check_functionality(client
->adapter
,
519 I2C_FUNC_SMBUS_READ_I2C_BLOCK
)) {
520 use_smbus
= I2C_SMBUS_I2C_BLOCK_DATA
;
521 } else if (i2c_check_functionality(client
->adapter
,
522 I2C_FUNC_SMBUS_READ_WORD_DATA
)) {
523 use_smbus
= I2C_SMBUS_WORD_DATA
;
524 } else if (i2c_check_functionality(client
->adapter
,
525 I2C_FUNC_SMBUS_READ_BYTE_DATA
)) {
526 use_smbus
= I2C_SMBUS_BYTE_DATA
;
528 return -EPFNOSUPPORT
;
532 /* Use I2C operations unless we're stuck with SMBus extensions. */
533 if (!i2c_check_functionality(client
->adapter
, I2C_FUNC_I2C
)) {
534 if (i2c_check_functionality(client
->adapter
,
535 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK
)) {
536 use_smbus_write
= I2C_SMBUS_I2C_BLOCK_DATA
;
537 } else if (i2c_check_functionality(client
->adapter
,
538 I2C_FUNC_SMBUS_WRITE_BYTE_DATA
)) {
539 use_smbus_write
= I2C_SMBUS_BYTE_DATA
;
544 if (chip
.flags
& AT24_FLAG_TAKE8ADDR
)
547 num_addresses
= DIV_ROUND_UP(chip
.byte_len
,
548 (chip
.flags
& AT24_FLAG_ADDR16
) ? 65536 : 256);
550 at24
= devm_kzalloc(&client
->dev
, sizeof(struct at24_data
) +
551 num_addresses
* sizeof(struct i2c_client
*), GFP_KERNEL
);
555 mutex_init(&at24
->lock
);
556 at24
->use_smbus
= use_smbus
;
557 at24
->use_smbus_write
= use_smbus_write
;
559 at24
->num_addresses
= num_addresses
;
562 * Export the EEPROM bytes through sysfs, since that's convenient.
563 * By default, only root should see the data (maybe passwords etc)
565 sysfs_bin_attr_init(&at24
->bin
);
566 at24
->bin
.attr
.name
= "eeprom";
567 at24
->bin
.attr
.mode
= chip
.flags
& AT24_FLAG_IRUGO
? S_IRUGO
: S_IRUSR
;
568 at24
->bin
.read
= at24_bin_read
;
569 at24
->bin
.size
= chip
.byte_len
;
571 at24
->macc
.read
= at24_macc_read
;
573 writable
= !(chip
.flags
& AT24_FLAG_READONLY
);
575 if (!use_smbus
|| use_smbus_write
) {
577 unsigned write_max
= chip
.page_size
;
579 at24
->macc
.write
= at24_macc_write
;
581 at24
->bin
.write
= at24_bin_write
;
582 at24
->bin
.attr
.mode
|= S_IWUSR
;
584 if (write_max
> io_limit
)
585 write_max
= io_limit
;
586 if (use_smbus
&& write_max
> I2C_SMBUS_BLOCK_MAX
)
587 write_max
= I2C_SMBUS_BLOCK_MAX
;
588 at24
->write_max
= write_max
;
590 /* buffer (data + address at the beginning) */
591 at24
->writebuf
= devm_kzalloc(&client
->dev
,
592 write_max
+ 2, GFP_KERNEL
);
596 dev_warn(&client
->dev
,
597 "cannot write due to controller restrictions.");
601 at24
->client
[0] = client
;
603 /* use dummy devices for multiple-address chips */
604 for (i
= 1; i
< num_addresses
; i
++) {
605 at24
->client
[i
] = i2c_new_dummy(client
->adapter
,
607 if (!at24
->client
[i
]) {
608 dev_err(&client
->dev
, "address 0x%02x unavailable\n",
615 err
= sysfs_create_bin_file(&client
->dev
.kobj
, &at24
->bin
);
619 i2c_set_clientdata(client
, at24
);
621 dev_info(&client
->dev
, "%zu byte %s EEPROM, %s, %u bytes/write\n",
622 at24
->bin
.size
, client
->name
,
623 writable
? "writable" : "read-only", at24
->write_max
);
624 if (use_smbus
== I2C_SMBUS_WORD_DATA
||
625 use_smbus
== I2C_SMBUS_BYTE_DATA
) {
626 dev_notice(&client
->dev
, "Falling back to %s reads, "
627 "performance will suffer\n", use_smbus
==
628 I2C_SMBUS_WORD_DATA
? "word" : "byte");
631 /* export data to kernel code */
633 chip
.setup(&at24
->macc
, chip
.context
);
638 for (i
= 1; i
< num_addresses
; i
++)
640 i2c_unregister_device(at24
->client
[i
]);
645 static int at24_remove(struct i2c_client
*client
)
647 struct at24_data
*at24
;
650 at24
= i2c_get_clientdata(client
);
651 sysfs_remove_bin_file(&client
->dev
.kobj
, &at24
->bin
);
653 for (i
= 1; i
< at24
->num_addresses
; i
++)
654 i2c_unregister_device(at24
->client
[i
]);
659 /*-------------------------------------------------------------------------*/
661 static struct i2c_driver at24_driver
= {
666 .remove
= at24_remove
,
667 .id_table
= at24_ids
,
670 static int __init
at24_init(void)
673 pr_err("at24: io_limit must not be 0!\n");
677 io_limit
= rounddown_pow_of_two(io_limit
);
678 return i2c_add_driver(&at24_driver
);
680 module_init(at24_init
);
682 static void __exit
at24_exit(void)
684 i2c_del_driver(&at24_driver
);
686 module_exit(at24_exit
);
688 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
689 MODULE_AUTHOR("David Brownell and Wolfram Sang");
690 MODULE_LICENSE("GPL");