Re: [PATCH 2/2] omap i2c: add a timeout to the busy waiting

[Aaro Koskinen <aaro.koskinen-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org>]

Hi,

Sonasath, Moiz wrote:
>> From: Menon, Nishanth
>> Alexander Shishkin said the following on 12/17/2009 07:01 PM:
>>> Well, I could calculate the timeout value based on current operating
>> speed,
>>> I guess. Or a delay. Perhaps OMAP_I2C_TIMEOUT can be used here?
>>>
>> it might be an overkill trying to generate counter based on opp speeds.
>> wondering if this delay is required in the first place..
> 
> The reason why this timeout was not put in place was that if the I2C
> controller is functional, the XUDF has to set after XRDY/XDR are set,
> the only case where it might not be set is when there is a sudden
> NACK | AL condition produced on the bus and the transfer stops
> (thereby the FIFO is not getting empty). The code takes care of this
> error situation so IMHO we can do without a timeout here.

We are able to reproduce an error situation, where none of XUDF|NACK|AL
gets set. In that case the kernel hangs. If we add the timeout, we are
able to recover. If you want to have a robust driver, you cannot have a
loop which is not guaranteed to terminate.

A.