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From: Grant Likely <grant.likely@secretlab.ca>
Date: Tue, 30 Jun 2009 13:08:30 -0600
Message-ID: <fa686aa40906301208p38f5c8deqc21ad8e423f0f4a8@mail.gmail.com>
Subject: Re: [PATCH] alsa/soc: add locking to mpc5200-psc-ac97 driver
To: Jon Smirl <jonsmirl@gmail.com>
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On Tue, Jun 30, 2009 at 12:33 PM, Jon Smirl<jonsmirl@gmail.com> wrote:
> On Tue, Jun 30, 2009 at 12:50 PM, Grant Likely<grant.likely@secretlab.ca>=
 wrote:
>> On Tue, Jun 30, 2009 at 12:18 AM, Wolfram Sang<w.sang@pengutronix.de> wr=
ote:
>>>> +
>>>> + =A0 =A0 /* Force clear the data valid bit */
>>>> + =A0 =A0 in_be32(&psc_dma->psc_regs->ac97_data);
>>>> +
>>>
>>> No mutex involved here. I think this is either a separate patch or it n=
eeds at
>>> least to be mentioned in the patch description.
>>
>> Oops, that was sloppy. =A0Yes, I'll put this into a separate patch. =A0T=
hanks.
>
> Now that you have added the mutexes, do you ever need to force clear
> the valid bit?
> Maybe log an error if this happens so that we can track down why.

I know exactly why it happened.  spin_event_timeout() had a bug that
would cause it to report a false positive timeout.  The bug is fixed
and queued for merging.

However, I still think this explicit clear should be applied.  It is
just a cheap register read and it prevents the driver from getting
wedged after a timeout does event, for whatever reason.

g.

--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.