Regression: at24 eeprom writing

Christian Gmeiner christian.gmeiner at
Sun Oct 4 23:16:56 PDT 2015

Hi Peter.

Sorry for the late answer - I am currently on my way to Dublin. Maybe
it helps if you enable
I2C_DEBUG_CORE and I2C_DEBUG_BUS. In theory you should see a little
bit better what
happens on the bus.

Christian Gmeiner, MSc

2015-10-04 21:50 GMT+02:00 Peter Rosin <peda at>:
> On 2015-10-03 01:05, Peter Rosin wrote:
>> I looked around and found that if I revert a839ce663b3183209fdf7b1fc4796bfe2a4679c3
>> "eeprom: at24: extend driver to allow writing via i2c_smbus_write_byte_data"
>> eeprom writing starts working again.
>> AFAICT, the i2c-at91 bus driver makes the eeprom driver use the
>> i2c_transfer code path both with that patch and with it reverted,
>> so I sadly don't see why the patch makes a difference.
> And now when I retry the same thing, that patch is no longer affecting things.
> I must have confused myself over what kernel was actually running. Christian,
> please accept my deepest apologies for implicating you in this regression.
> But the regression is still there. In short, linux-3.18-at91 from the
> linux4sam tree works, linux-4.1-at91 from the same tree does not, and
> vanilla 4.2 also doesn't work. I have a hard time bisecting this thing
> though, since the last known good version has a long list of atmel
> patches that I refuse to even try to rebase...
> Ideas still welcome of course.
> Cheers,
> Peter

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