[alsa-devel] system suspend and live audio streams

Mark Brown broonie at opensource.wolfsonmicro.com
Mon Apr 16 14:24:27 CEST 2012

On Mon, Apr 16, 2012 at 01:40:41PM +0300, Peter Ujfalusi wrote:

> What we need to do is to have proper register store/restore for McBSP to
> support suspend during audio activity. But. Even with that if the McBSP
> is hitting OFF mode we will loose the McBSP FIFO content (invalidated).
> This means we are going to have missing samples. Probably the user will
> not going to notice it, but it is going to happen.

> I'm sure this issue present on other platforms as well. The pm_runtime
> is handled by the core, we should have suspend/resume checked in ASoC
> core, if there's an issue we need to fix it. After that the McBSP
> store/restore need to be implemented.

If the driver is using runtime PM and needs to ensure that a reference
is held outside of audio streaming then it should be taking care of
holding a reference itself.

Tegra is now handling this using the regmap cache infrastructure to make
the device powerdown transparent.

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