[alsa-devel] [PATCH 1/3] ASoC: davinci-pcm: latch EDMA errors

Ben Gardiner bengardiner at nanometrics.ca
Tue Oct 4 04:04:29 CEST 2011

Hi Mark,

Thank you for offering your insights.

On Sun, Oct 2, 2011 at 2:48 PM, Mark Brown
<broonie at opensource.wolfsonmicro.com> wrote:
> On Fri, Sep 30, 2011 at 05:23:01PM -0400, Ben Gardiner wrote:
>> The davinci-pcm driver currently ignores all EDMA completion callbacks that
>> could be indicating an error.
>> Latch any edma error-status callbacks and report them as SNDDRV_PCM_POS_XRUN
>> like is done in fsl_dma.c.
> Nothing in this patch ever seems to clear the flag which seems rather
> extreme.  I'd expect that if you're going to do this then the flag would
> be cleared after one error has been reported.

Ok. I think you have impressed upon me the intent of the _POS_XRUN
retum -- i see now that it should not be latched. I will fix this in
spin 2.

>> In testing when an error occured early-on in playback the stream did not halt,
>> but several underruns were reported until eventually the stream halted.
>> Is there a better way to report HW errors up the stack?
> Not really, and it's not clear that it's constructive to try -  if
> there's a problem that doesn't otherwise cause a failure then generally
> the user will intervene.

Again, thank you for your insight. My understanding now is that
_POS_XRUN is _the_ way to report HW errors and that it is up to the
application to determine the consequences of an xrun.

Best Regards,
Ben Gardiner

Nanometrics Inc.

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