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eeprom: at24: support reading the serial number for 24csxx

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The chips from the at24cs family have two memory areas - a regular
read-write block and a read-only area containing the serial number.

The latter is visible on a different slave address (the address of the
rw memory block + 0x08). In order to access both blocks the user needs
to instantiate a regular at24c device for the rw block address and a
corresponding at24cs device on the serial number block address.

Add a function that allows to access the serial number and assign it
to at24->read_func if the chip allows serial number read operations
and the driver was passed the relevant flag for this device.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Bartosz Golaszewski 2016-06-06 10:48:51 +02:00 committed by Wolfram Sang
parent a7284a82e8
commit 818d0220d8
2 changed files with 79 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

80
drivers/misc/eeprom/at24.c
View file

@ -134,16 +134,34 @@ static const struct i2c_device_id at24_ids[] = {
{ "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
/* old variants can't be handled with this generic entry! */
{ "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
{ "24cs01", AT24_DEVICE_MAGIC(16,
AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
{ "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
{ "24cs02", AT24_DEVICE_MAGIC(16,
AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
/* spd is a 24c02 in memory DIMMs */
{ "spd", AT24_DEVICE_MAGIC(2048 / 8,
AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
{ "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
{ "24cs04", AT24_DEVICE_MAGIC(16,
AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
/* 24rf08 quirk is handled at i2c-core */
{ "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
{ "24cs08", AT24_DEVICE_MAGIC(16,
AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
{ "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
{ "24cs16", AT24_DEVICE_MAGIC(16,
AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
{ "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
{ "24cs32", AT24_DEVICE_MAGIC(16,
AT24_FLAG_ADDR16 |
AT24_FLAG_SERIAL |
AT24_FLAG_READONLY) },
{ "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
{ "24cs64", AT24_DEVICE_MAGIC(16,
AT24_FLAG_ADDR16 |
AT24_FLAG_SERIAL |
AT24_FLAG_READONLY) },
{ "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
{ "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
{ "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
@ -276,6 +294,59 @@ static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf,
return -ETIMEDOUT;
}
static ssize_t at24_eeprom_read_serial(struct at24_data *at24, char *buf,
unsigned int offset, size_t count)
{
unsigned long timeout, read_time;
struct i2c_client *client;
struct i2c_msg msg[2];
u8 addrbuf[2];
int status;
client = at24_translate_offset(at24, &offset);
memset(msg, 0, sizeof(msg));
msg[0].addr = client->addr;
msg[0].buf = addrbuf;
/*
* The address pointer of the device is shared between the regular
* EEPROM array and the serial number block. The dummy write (part of
* the sequential read protocol) ensures the address pointer is reset
* to the desired position.
*/
if (at24->chip.flags & AT24_FLAG_ADDR16) {
/*
* For 16 bit address pointers, the word address must contain
* a '10' sequence in bits 11 and 10 regardless of the
* intended position of the address pointer.
*/
addrbuf[0] = 0x08;
addrbuf[1] = offset;
msg[0].len = 2;
} else {
/*
* Otherwise the word address must begin with a '10' sequence,
* regardless of the intended address.
*/
addrbuf[0] = 0x80 + offset;
msg[0].len = 1;
}
msg[1].addr = client->addr;
msg[1].flags = I2C_M_RD;
msg[1].buf = buf;
msg[1].len = count;
loop_until_timeout(timeout, read_time) {
status = i2c_transfer(client->adapter, msg, 2);
if (status == 2)
return count;
}
return -ETIMEDOUT;
}
/*
* Note that if the hardware write-protect pin is pulled high, the whole
* chip is normally write protected. But there are plenty of product
@ -577,8 +648,13 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
at24->chip = chip;
at24->num_addresses = num_addresses;
at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
: at24_eeprom_read_i2c;
if (chip.flags & AT24_FLAG_SERIAL) {
at24->read_func = at24_eeprom_read_serial;
} else {
at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus
: at24_eeprom_read_i2c;
}
if (at24->use_smbus) {
if (at24->use_smbus_write == I2C_SMBUS_I2C_BLOCK_DATA)
at24->write_func = at24_eeprom_write_smbus_block;

1
include/linux/platform_data/at24.h
View file

@ -48,6 +48,7 @@ struct at24_platform_data {
#define AT24_FLAG_READONLY BIT(6) /* sysfs-entry will be read-only */
#define AT24_FLAG_IRUGO BIT(5) /* sysfs-entry will be world-readable */
#define AT24_FLAG_TAKE8ADDR BIT(4) /* take always 8 addresses (24c00) */
#define AT24_FLAG_SERIAL BIT(3) /* factory-programmed serial number */
void (*setup)(struct nvmem_device *nvmem, void *context);
void *context;