Re: [PATCH i2c-next 1/2] dt-bindings: i2c: aspeed: add hardware timeout support

Jae Hyun Yoo
2019-10-22T17:09:06Z

On 10/21/2019 9:56 PM, Wolfram Sang wrote:
>
>> Changes I submitted in this patch set is for a different purpose which
>> is very Aspeed H/W specific, and actually it's a more serious timeout
>> setting indeed. If this H/W is used in multi-master environment, it
>> could meet a H/W hang that freezes itself in slave mode and it can't
>> escape from the state. To resolve the specific case, this H/W provides
>> self-recovery feature which monitors abnormal state of SDA, SCL and its
>> H/W state machine using the timeout setting to determine the escape
>> condition.
>
> Thanks for the summary. I just wonder on what the timeout value depends.
> Do we really need to put in DT or can we derive it e.g. from the
> compatible value in the driver?

It could be derived from the bus timeout value by computing 'divide by
x' roughly but it couldn't cover all use cases because this H/W timeout
value would depends on each environment. There are many factors that
can affect it such as bus speed, peer-master's bus driving
characteristic, average transaction period on the bus and so on thus
it may need fine adjustments through a DT setting, I think.

Thanks,

Jae