[alsa-devel] [PATCH V1 2/3] ASoC: fsl_spdif: spba clk is needed by spdif device

[Shengjiu Wang]

On Sat, Sep 19, 2015 at 06:50:40AM -0700, Mark Brown wrote:
> On Thu, Sep 17, 2015 at 10:54:08AM -0700, Nicolin Chen wrote:
> > On Thu, Sep 17, 2015 at 12:01:54PM +0100, Mark Brown wrote:
> > > On Thu, Sep 17, 2015 at 02:09:24PM +0800, Shengjiu Wang wrote:
> 
> > > > +	"dma"		  The spba clock is needed when sdma share peripheral
> > > > +			  script is used.
> 
> > > It sounds like this clock is used by the DMA controller - shouldn't the
> > > DMA controller driver be responsible for enabling it?
> 
> > I agree but it doesn't seems to be easy to enable and disable it
> > dynamically along with ASoC open() and close() functions as the
> > current clocks of SDMA get enabled when its channels are allocated
> > during the system boot-up via generic DMA bindings.
> 
> Do we need to do things along with open() and close() or wouldn't doing
> things along with the DMA operatiosn suffice?
> 
> > Maybe we can put in the issue_pending() and terminate_all() which
> > are regularly called along with ASoC trigger(), or just open it
> > permanently if the penalty of power efficiency is ignorable.
> 
> Or some kind of runtime PM usage within the DMA driver (possibly at
> those points)?  It does seem like something we should solve in the DMA
> code rather than in generic code.
> 

I think spba clock should be used by the audio IP not DMA, because in same
situation the FSL_SSI doesn't need this clock.

best regards
wang shengjiu