mt7621 i2c fails with upstream driver

mt7621 i2c fails with upstream driver

[Kristian Evensen]

Hello,

I am in the process of bringing kernel 5.10 up on an mt7621-based
board. The board is equipped with a temperature sensor that is
connected to the i2c bus. Reading the temperature worked fine with my
previous kernel (OpenWRT 4.14/downstream i2c driver), but fails when I
use the upstream driver.

With the 5.10 i2c-mt7621-driver, i2cdetect is no longer able to detect
the sensor and i2cget fails with "Error: Read failed". An strace of
i2cget reveals the cause to be the final ioctl call failing with
ETIMEDOUT.

Replacing the new with the old driver makes i2c work again, but I
would like to try to avoid that. My knowledge of i2c is very limited,
so I wondered if anyone knows what could be wrong or have any
suggestions on things I can try to for example change in the driver?

Thanks in advance for any help,
Kristian

Re: mt7621 i2c fails with upstream driver

[Kristian Evensen]

Hi again,

On Wed, Jan 5, 2022 at 10:51 AM Kristian Evensen
<kristian.evensen@gmail.com> wrote:
> Replacing the new with the old driver makes i2c work again, but I
> would like to try to avoid that. My knowledge of i2c is very limited,
> so I wondered if anyone knows what could be wrong or have any
> suggestions on things I can try to for example change in the driver?

I spent some more time instrumenting the driver. The call that always
times out is the call to mtk_i2c_master_start() made from
mtk_i2c_master_xfer(). From what I can tell, this is the first time
data is written and when I compared with the previous driver, I do not
find equivalents of master_{start,stop,cmd} writes, I only see direct
calls to iowrite/ioread.

Kristian

Re: mt7621 i2c fails with upstream driver

[Wolfram Sang]

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Adding maintainers for this driver/platform to CC...

On Wed, Jan 05, 2022 at 10:51:38AM +0100, Kristian Evensen wrote:
> Hello,
> 
> I am in the process of bringing kernel 5.10 up on an mt7621-based
> board. The board is equipped with a temperature sensor that is
> connected to the i2c bus. Reading the temperature worked fine with my
> previous kernel (OpenWRT 4.14/downstream i2c driver), but fails when I
> use the upstream driver.
> 
> With the 5.10 i2c-mt7621-driver, i2cdetect is no longer able to detect
> the sensor and i2cget fails with "Error: Read failed". An strace of
> i2cget reveals the cause to be the final ioctl call failing with
> ETIMEDOUT.
> 
> Replacing the new with the old driver makes i2c work again, but I
> would like to try to avoid that. My knowledge of i2c is very limited,
> so I wondered if anyone knows what could be wrong or have any
> suggestions on things I can try to for example change in the driver?
> 
> Thanks in advance for any help,
> Kristian

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