[alsa-devel] [PATCH] ASoC: dapm: check suspend state in dapm_dai_check_power()

[Lars-Peter Clausen]

On 06/03/2013 08:51 PM, Mark Brown wrote:
> On Mon, Jun 03, 2013 at 11:36:40AM -0600, Stephen Warren wrote:
>> From: Stephen Warren <swarren at nvidia.com>
>>
>> Currently, when the system enters suspend with audio playing, since the
>> DAI widgets are active, the associated CODEC is considered active, and
>> hence is not transition into a low-power bias state as the system
>> suspends. This likely causes audio failure after resume, since the CODEC
>> power has quite possibly been removed during suspend, and the bias level
>> transitions in the CODEC driver are needed to recover from this. At the
>> very least, this issue likely causes warnings in the kernel log due to
>> the CODEC being left on over the suspend transition.
>>
>> To solve this, modify dapm_dai_check_power() not to consider DAI widgets
>> active if the system is entering suspend.
> 
> I would expect us to be dealing with this as part of quiescing the DMA
> operations on the links - it's not just the CODEC that needs handling
> here.  This feels like it ought to be more joined up somewhere along the
> line.

I think it is just an oversight that this is not working properly right now.
In snd_soc_suspend() where we also stop the DMA streams etc the DAI link
widgets are put into suspend, by calling snd_soc_dapm_stream_event(...,
SND_SOC_DAPM_STREAM_SUSPEND). But dapm_dai_check_power() doesn't consider
this and hence stays active and also keeps the whole DAPM context (this is
not CODEC specific) active.

- Lars