[alsa-devel] [PATCH 1/4] ASoC:rt5670:Add runtime PM support

[Lin, Mengdong]

> -----Original Message-----
> From: Mark Brown [mailto:broonie at kernel.org]
> Sent: Thursday, November 06, 2014 1:55 PM
> To: bardliao at realtek.com

> > +static int rt5670_runtime_resume(struct device *dev) {
> > +	return 0;
> > +}
> 
> This should be undoing the change done on suspend otherwise we'll be stuck
> on the internal clock after resuming.  Alternatively if something will undo that
> elsewhere then presumably we don't need to use runtime PM to select the
> internal clock anyway?

Is it okay to restore default sysclock setting is runtime_resume ops?

The codec sysclk source is MCLK (PLL is powered down) after boot by default.
We can also apply this when runtime resuming.

On Intel CherryTrail/Braswell platform, the BIOS will always restore MCLK when
the codec resumes from D3 to D0. So it's safe to use MCLK as source for codec 
sysclk in runtime_resume ops. And later hw_params ops can further configure 
sysclk source and PLL for active audio streaming.

Thanks
Mengdong