[PATCH] misc: i2c_eeprom: fix at24c32 offset_len

[Eugen Hristev]

According to at24c32 datasheet:

RANDOM READ: A random read requires a “dummy” byte write sequence to load in
the dataword address. Once the device address word and data word address are
clocked in and acknowledged by the EEPROM, the microcontroller must generate
another start condition.

BYTE WRITE: A write operation requires two 8-bit data word addresses following
the device address word and acknowledgment. Upon receipt of this address, the
EEPROM will again respond with a zero and then clock in the first 8-bit data
word.

>From this, my understanding is that dataword is 1 byte, and when reading the
offset is just 1 byte.

By having an offset len of 2 bytes, reading from the eeprom at boot time to
read the stored MAC address fails on sam9x60ek board which has this eeprom.

When changing the offset len to 1 byte, reading the MAC address from the offset
inside the EEPROM works correctly.

Fixes: 821c982e35 ("misc: i2c_eeprom: set offset len and chip addr offset mask")
Reported-by: Sergiu Moga <sergiu.moga at microchip.com>
Signed-off-by: Eugen Hristev <eugen.hristev at microchip.com>
Tested-by: Claudiu Beznea <claudiu.beznea at microchip.com>
---

Hi everyone,

We tested this on sam9x60ek board. I see in DT that various other boards
use this eeprom.
I have added several people to the patch e-mail, however not comprehensively
everyone.
I do not wish to affect functionality for other boards, even though this
patch appears correct.
Some other tests would be welcome, on other boards having this EEPROM.

Thanks!
Eugen

 drivers/misc/i2c_eeprom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/i2c_eeprom.c b/drivers/misc/i2c_eeprom.c
index 89a450d0f8..c8c67cf028 100644
--- a/drivers/misc/i2c_eeprom.c
+++ b/drivers/misc/i2c_eeprom.c
@@ -230,7 +230,7 @@ static const struct i2c_eeprom_drv_data atmel24c32_data = {
 	.size = 4096,
 	.pagesize = 32,
 	.addr_offset_mask = 0,
-	.offset_len = 2,
+	.offset_len = 1,
 };
 
 static const struct i2c_eeprom_drv_data atmel24c64_data = {
-- 
2.25.1