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/acpi.h>
25 #include <linux/i2c.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
;
58 struct memory_accessor macc
;
63 * Lock protects against activities from other Linux tasks,
64 * but not from changes by other I2C masters.
67 struct bin_attribute bin
;
71 unsigned num_addresses
;
74 * Some chips tie up multiple I2C addresses; dummy devices reserve
75 * them for us, and we'll use them with SMBus calls.
77 struct i2c_client
*client
[];
81 * This parameter is to help this driver avoid blocking other drivers out
82 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
83 * clock, one 256 byte read takes about 1/43 second which is excessive;
84 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
85 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
87 * This value is forced to be a power of two so that writes align on pages.
89 static unsigned io_limit
= 128;
90 module_param(io_limit
, uint
, 0);
91 MODULE_PARM_DESC(io_limit
, "Maximum bytes per I/O (default 128)");
94 * Specs often allow 5 msec for a page write, sometimes 20 msec;
95 * it's important to recover from write timeouts.
97 static unsigned write_timeout
= 25;
98 module_param(write_timeout
, uint
, 0);
99 MODULE_PARM_DESC(write_timeout
, "Time (in ms) to try writes (default 25)");
101 #define AT24_SIZE_BYTELEN 5
102 #define AT24_SIZE_FLAGS 8
104 #define AT24_BITMASK(x) (BIT(x) - 1)
106 /* create non-zero magic value for given eeprom parameters */
107 #define AT24_DEVICE_MAGIC(_len, _flags) \
108 ((1 << AT24_SIZE_FLAGS | (_flags)) \
109 << AT24_SIZE_BYTELEN | ilog2(_len))
111 static const struct i2c_device_id at24_ids
[] = {
112 /* needs 8 addresses as A0-A2 are ignored */
113 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR
) },
114 /* old variants can't be handled with this generic entry! */
115 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
116 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
117 /* spd is a 24c02 in memory DIMMs */
118 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
119 AT24_FLAG_READONLY
| AT24_FLAG_IRUGO
) },
120 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
121 /* 24rf08 quirk is handled at i2c-core */
122 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
123 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
124 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16
) },
125 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16
) },
126 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16
) },
127 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16
) },
128 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16
) },
129 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16
) },
131 { /* END OF LIST */ }
133 MODULE_DEVICE_TABLE(i2c
, at24_ids
);
135 static const struct acpi_device_id at24_acpi_ids
[] = {
136 { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
139 MODULE_DEVICE_TABLE(acpi
, at24_acpi_ids
);
141 /*-------------------------------------------------------------------------*/
144 * This routine supports chips which consume multiple I2C addresses. It
145 * computes the addressing information to be used for a given r/w request.
146 * Assumes that sanity checks for offset happened at sysfs-layer.
148 static struct i2c_client
*at24_translate_offset(struct at24_data
*at24
,
153 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
) {
161 return at24
->client
[i
];
164 static ssize_t
at24_eeprom_read(struct at24_data
*at24
, char *buf
,
165 unsigned offset
, size_t count
)
167 struct i2c_msg msg
[2];
169 struct i2c_client
*client
;
170 unsigned long timeout
, read_time
;
173 memset(msg
, 0, sizeof(msg
));
176 * REVISIT some multi-address chips don't rollover page reads to
177 * the next slave address, so we may need to truncate the count.
178 * Those chips might need another quirk flag.
180 * If the real hardware used four adjacent 24c02 chips and that
181 * were misconfigured as one 24c08, that would be a similar effect:
182 * one "eeprom" file not four, but larger reads would fail when
183 * they crossed certain pages.
187 * Slave address and byte offset derive from the offset. Always
188 * set the byte address; on a multi-master board, another master
189 * may have changed the chip's "current" address pointer.
191 client
= at24_translate_offset(at24
, &offset
);
193 if (count
> io_limit
)
196 if (at24
->use_smbus
) {
197 /* Smaller eeproms can work given some SMBus extension calls */
198 if (count
> I2C_SMBUS_BLOCK_MAX
)
199 count
= I2C_SMBUS_BLOCK_MAX
;
202 * When we have a better choice than SMBus calls, use a
203 * combined I2C message. Write address; then read up to
204 * io_limit data bytes. Note that read page rollover helps us
205 * here (unlike writes). msgbuf is u8 and will cast to our
209 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
)
210 msgbuf
[i
++] = offset
>> 8;
211 msgbuf
[i
++] = offset
;
213 msg
[0].addr
= client
->addr
;
217 msg
[1].addr
= client
->addr
;
218 msg
[1].flags
= I2C_M_RD
;
224 * Reads fail if the previous write didn't complete yet. We may
225 * loop a few times until this one succeeds, waiting at least
226 * long enough for one entire page write to work.
228 timeout
= jiffies
+ msecs_to_jiffies(write_timeout
);
231 if (at24
->use_smbus
) {
232 status
= i2c_smbus_read_i2c_block_data_or_emulated(client
, offset
,
235 status
= i2c_transfer(client
->adapter
, msg
, 2);
239 dev_dbg(&client
->dev
, "read %zu@%d --> %d (%ld)\n",
240 count
, offset
, status
, jiffies
);
245 /* REVISIT: at HZ=100, this is sloooow */
247 } while (time_before(read_time
, timeout
));
252 static ssize_t
at24_read(struct at24_data
*at24
,
253 char *buf
, loff_t off
, size_t count
)
257 if (unlikely(!count
))
261 * Read data from chip, protecting against concurrent updates
262 * from this host, but not from other I2C masters.
264 mutex_lock(&at24
->lock
);
269 status
= at24_eeprom_read(at24
, buf
, off
, count
);
281 mutex_unlock(&at24
->lock
);
286 static ssize_t
at24_bin_read(struct file
*filp
, struct kobject
*kobj
,
287 struct bin_attribute
*attr
,
288 char *buf
, loff_t off
, size_t count
)
290 struct at24_data
*at24
;
292 at24
= dev_get_drvdata(container_of(kobj
, struct device
, kobj
));
293 return at24_read(at24
, buf
, off
, count
);
298 * Note that if the hardware write-protect pin is pulled high, the whole
299 * chip is normally write protected. But there are plenty of product
300 * variants here, including OTP fuses and partial chip protect.
302 * We only use page mode writes; the alternative is sloooow. This routine
303 * writes at most one page.
305 static ssize_t
at24_eeprom_write(struct at24_data
*at24
, const char *buf
,
306 unsigned offset
, size_t count
)
308 struct i2c_client
*client
;
311 unsigned long timeout
, write_time
;
314 /* Get corresponding I2C address and adjust offset */
315 client
= at24_translate_offset(at24
, &offset
);
317 /* write_max is at most a page */
318 if (count
> at24
->write_max
)
319 count
= at24
->write_max
;
321 /* Never roll over backwards, to the start of this page */
322 next_page
= roundup(offset
+ 1, at24
->chip
.page_size
);
323 if (offset
+ count
> next_page
)
324 count
= next_page
- offset
;
326 /* If we'll use I2C calls for I/O, set up the message */
327 if (!at24
->use_smbus
) {
330 msg
.addr
= client
->addr
;
333 /* msg.buf is u8 and casts will mask the values */
334 msg
.buf
= at24
->writebuf
;
335 if (at24
->chip
.flags
& AT24_FLAG_ADDR16
)
336 msg
.buf
[i
++] = offset
>> 8;
338 msg
.buf
[i
++] = offset
;
339 memcpy(&msg
.buf
[i
], buf
, count
);
344 * Writes fail if the previous one didn't complete yet. We may
345 * loop a few times until this one succeeds, waiting at least
346 * long enough for one entire page write to work.
348 timeout
= jiffies
+ msecs_to_jiffies(write_timeout
);
350 write_time
= jiffies
;
351 if (at24
->use_smbus_write
) {
352 switch (at24
->use_smbus_write
) {
353 case I2C_SMBUS_I2C_BLOCK_DATA
:
354 status
= i2c_smbus_write_i2c_block_data(client
,
357 case I2C_SMBUS_BYTE_DATA
:
358 status
= i2c_smbus_write_byte_data(client
,
366 status
= i2c_transfer(client
->adapter
, &msg
, 1);
370 dev_dbg(&client
->dev
, "write %zu@%d --> %zd (%ld)\n",
371 count
, offset
, status
, jiffies
);
376 /* REVISIT: at HZ=100, this is sloooow */
378 } while (time_before(write_time
, timeout
));
383 static ssize_t
at24_write(struct at24_data
*at24
, const char *buf
, loff_t off
,
388 if (unlikely(!count
))
392 * Write data to chip, protecting against concurrent updates
393 * from this host, but not from other I2C masters.
395 mutex_lock(&at24
->lock
);
400 status
= at24_eeprom_write(at24
, buf
, off
, count
);
412 mutex_unlock(&at24
->lock
);
417 static ssize_t
at24_bin_write(struct file
*filp
, struct kobject
*kobj
,
418 struct bin_attribute
*attr
,
419 char *buf
, loff_t off
, size_t count
)
421 struct at24_data
*at24
;
423 at24
= dev_get_drvdata(container_of(kobj
, struct device
, kobj
));
424 return at24_write(at24
, buf
, off
, count
);
427 /*-------------------------------------------------------------------------*/
430 * This lets other kernel code access the eeprom data. For example, it
431 * might hold a board's Ethernet address, or board-specific calibration
432 * data generated on the manufacturing floor.
435 static ssize_t
at24_macc_read(struct memory_accessor
*macc
, char *buf
,
436 off_t offset
, size_t count
)
438 struct at24_data
*at24
= container_of(macc
, struct at24_data
, macc
);
440 return at24_read(at24
, buf
, offset
, count
);
443 static ssize_t
at24_macc_write(struct memory_accessor
*macc
, const char *buf
,
444 off_t offset
, size_t count
)
446 struct at24_data
*at24
= container_of(macc
, struct at24_data
, macc
);
448 return at24_write(at24
, buf
, offset
, count
);
451 /*-------------------------------------------------------------------------*/
454 static void at24_get_ofdata(struct i2c_client
*client
,
455 struct at24_platform_data
*chip
)
458 struct device_node
*node
= client
->dev
.of_node
;
461 if (of_get_property(node
, "read-only", NULL
))
462 chip
->flags
|= AT24_FLAG_READONLY
;
463 val
= of_get_property(node
, "pagesize", NULL
);
465 chip
->page_size
= be32_to_cpup(val
);
469 static void at24_get_ofdata(struct i2c_client
*client
,
470 struct at24_platform_data
*chip
)
472 #endif /* CONFIG_OF */
474 static int at24_probe(struct i2c_client
*client
, const struct i2c_device_id
*id
)
476 struct at24_platform_data chip
;
477 kernel_ulong_t magic
= 0;
480 int use_smbus_write
= 0;
481 struct at24_data
*at24
;
483 unsigned i
, num_addresses
;
485 if (client
->dev
.platform_data
) {
486 chip
= *(struct at24_platform_data
*)client
->dev
.platform_data
;
489 magic
= id
->driver_data
;
491 const struct acpi_device_id
*aid
;
493 aid
= acpi_match_device(at24_acpi_ids
, &client
->dev
);
495 magic
= aid
->driver_data
;
500 chip
.byte_len
= BIT(magic
& AT24_BITMASK(AT24_SIZE_BYTELEN
));
501 magic
>>= AT24_SIZE_BYTELEN
;
502 chip
.flags
= magic
& AT24_BITMASK(AT24_SIZE_FLAGS
);
504 * This is slow, but we can't know all eeproms, so we better
505 * play safe. Specifying custom eeprom-types via platform_data
506 * is recommended anyhow.
510 /* update chipdata if OF is present */
511 at24_get_ofdata(client
, &chip
);
517 if (!is_power_of_2(chip
.byte_len
))
518 dev_warn(&client
->dev
,
519 "byte_len looks suspicious (no power of 2)!\n");
520 if (!chip
.page_size
) {
521 dev_err(&client
->dev
, "page_size must not be 0!\n");
524 if (!is_power_of_2(chip
.page_size
))
525 dev_warn(&client
->dev
,
526 "page_size looks suspicious (no power of 2)!\n");
528 /* Use I2C operations unless we're stuck with SMBus extensions. */
529 if (!i2c_check_functionality(client
->adapter
, I2C_FUNC_I2C
)) {
530 if (chip
.flags
& AT24_FLAG_ADDR16
)
531 return -EPFNOSUPPORT
;
533 if (i2c_check_functionality(client
->adapter
,
534 I2C_FUNC_SMBUS_READ_I2C_BLOCK
)) {
535 use_smbus
= I2C_SMBUS_I2C_BLOCK_DATA
;
536 } else if (i2c_check_functionality(client
->adapter
,
537 I2C_FUNC_SMBUS_READ_WORD_DATA
)) {
538 use_smbus
= I2C_SMBUS_WORD_DATA
;
539 } else if (i2c_check_functionality(client
->adapter
,
540 I2C_FUNC_SMBUS_READ_BYTE_DATA
)) {
541 use_smbus
= I2C_SMBUS_BYTE_DATA
;
543 return -EPFNOSUPPORT
;
547 /* Use I2C operations unless we're stuck with SMBus extensions. */
548 if (!i2c_check_functionality(client
->adapter
, I2C_FUNC_I2C
)) {
549 if (i2c_check_functionality(client
->adapter
,
550 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK
)) {
551 use_smbus_write
= I2C_SMBUS_I2C_BLOCK_DATA
;
552 } else if (i2c_check_functionality(client
->adapter
,
553 I2C_FUNC_SMBUS_WRITE_BYTE_DATA
)) {
554 use_smbus_write
= I2C_SMBUS_BYTE_DATA
;
559 if (chip
.flags
& AT24_FLAG_TAKE8ADDR
)
562 num_addresses
= DIV_ROUND_UP(chip
.byte_len
,
563 (chip
.flags
& AT24_FLAG_ADDR16
) ? 65536 : 256);
565 at24
= devm_kzalloc(&client
->dev
, sizeof(struct at24_data
) +
566 num_addresses
* sizeof(struct i2c_client
*), GFP_KERNEL
);
570 mutex_init(&at24
->lock
);
571 at24
->use_smbus
= use_smbus
;
572 at24
->use_smbus_write
= use_smbus_write
;
574 at24
->num_addresses
= num_addresses
;
577 * Export the EEPROM bytes through sysfs, since that's convenient.
578 * By default, only root should see the data (maybe passwords etc)
580 sysfs_bin_attr_init(&at24
->bin
);
581 at24
->bin
.attr
.name
= "eeprom";
582 at24
->bin
.attr
.mode
= chip
.flags
& AT24_FLAG_IRUGO
? S_IRUGO
: S_IRUSR
;
583 at24
->bin
.read
= at24_bin_read
;
584 at24
->bin
.size
= chip
.byte_len
;
586 at24
->macc
.read
= at24_macc_read
;
588 writable
= !(chip
.flags
& AT24_FLAG_READONLY
);
590 if (!use_smbus
|| use_smbus_write
) {
592 unsigned write_max
= chip
.page_size
;
594 at24
->macc
.write
= at24_macc_write
;
596 at24
->bin
.write
= at24_bin_write
;
597 at24
->bin
.attr
.mode
|= S_IWUSR
;
599 if (write_max
> io_limit
)
600 write_max
= io_limit
;
601 if (use_smbus
&& write_max
> I2C_SMBUS_BLOCK_MAX
)
602 write_max
= I2C_SMBUS_BLOCK_MAX
;
603 at24
->write_max
= write_max
;
605 /* buffer (data + address at the beginning) */
606 at24
->writebuf
= devm_kzalloc(&client
->dev
,
607 write_max
+ 2, GFP_KERNEL
);
611 dev_warn(&client
->dev
,
612 "cannot write due to controller restrictions.");
616 at24
->client
[0] = client
;
618 /* use dummy devices for multiple-address chips */
619 for (i
= 1; i
< num_addresses
; i
++) {
620 at24
->client
[i
] = i2c_new_dummy(client
->adapter
,
622 if (!at24
->client
[i
]) {
623 dev_err(&client
->dev
, "address 0x%02x unavailable\n",
630 err
= sysfs_create_bin_file(&client
->dev
.kobj
, &at24
->bin
);
634 i2c_set_clientdata(client
, at24
);
636 dev_info(&client
->dev
, "%zu byte %s EEPROM, %s, %u bytes/write\n",
637 at24
->bin
.size
, client
->name
,
638 writable
? "writable" : "read-only", at24
->write_max
);
639 if (use_smbus
== I2C_SMBUS_WORD_DATA
||
640 use_smbus
== I2C_SMBUS_BYTE_DATA
) {
641 dev_notice(&client
->dev
, "Falling back to %s reads, "
642 "performance will suffer\n", use_smbus
==
643 I2C_SMBUS_WORD_DATA
? "word" : "byte");
646 /* export data to kernel code */
648 chip
.setup(&at24
->macc
, chip
.context
);
653 for (i
= 1; i
< num_addresses
; i
++)
655 i2c_unregister_device(at24
->client
[i
]);
660 static int at24_remove(struct i2c_client
*client
)
662 struct at24_data
*at24
;
665 at24
= i2c_get_clientdata(client
);
666 sysfs_remove_bin_file(&client
->dev
.kobj
, &at24
->bin
);
668 for (i
= 1; i
< at24
->num_addresses
; i
++)
669 i2c_unregister_device(at24
->client
[i
]);
674 /*-------------------------------------------------------------------------*/
676 static struct i2c_driver at24_driver
= {
679 .acpi_match_table
= ACPI_PTR(at24_acpi_ids
),
682 .remove
= at24_remove
,
683 .id_table
= at24_ids
,
686 static int __init
at24_init(void)
689 pr_err("at24: io_limit must not be 0!\n");
693 io_limit
= rounddown_pow_of_two(io_limit
);
694 return i2c_add_driver(&at24_driver
);
696 module_init(at24_init
);
698 static void __exit
at24_exit(void)
700 i2c_del_driver(&at24_driver
);
702 module_exit(at24_exit
);
704 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
705 MODULE_AUTHOR("David Brownell and Wolfram Sang");
706 MODULE_LICENSE("GPL");