[alsa-devel] [PATCH v7] ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent glitches

[Peter Ujfalusi]

On 01/16/2017 09:30 PM, Matt Ranostay wrote:
> Yep I was testing with that enabled. Not sure why I'm not getting it
> all... maybe different side effects like sample rate of the audio
> being played?
> 
> Peter, is there chance that there is race condition is possible
> between pm_qos_remove_request and omap_mcbsp_dai_shutdown?

Not with my knowledge.
However one thing might happen which is not handled:
application opens up the audio card, does some hw_param setup, then it
decides to close the card. In this case the pm_qos is not placed, but in
dai_shutdown we try to remove it -> WARN().

I think we need to check either if the pm_qos is active and only then
bother with the removal/updated or we can check if the
mcbsp->latency[stream1] is not 0, which should be the same as checking
for the pm_qos active.

-- 
Péter