[alsa-devel] Choosing the sysclk in simple-card looks broken to me.

[Nicolin Chen]

On Mon, Aug 11, 2014 at 07:56:12AM -0400, jonsmirl at gmail.com wrote:
> > It looks like the problem is that Simple Card also configures cpu-dai
> > via set_sysclk() with direction SND_SOC_CLOCK_IN while it fetches the
> > sysclk rate not from MCLK source but from 'sound-dai' -- cpu-dai node
> > itself, when the binding for sound-dai doesn't have clock or frequency
> > assignment, although this fetching works out for codec-dai side.
> >
> > In your case, Simple Card sets both sides of dai with different sysclk
> > rates, and meanwhile the sysclk rate for cpu-dai is incorrect.
> >
> > Is it true?
> 
> Yes, that is what is going on.  Trying to use sgtl5000 with
> simple-audio exposed that issue. Without removing that 'else' clause
> there is no way to tell simple-audio just to leave the cpu-dai alone.

This issue remained in Simple Card shall be fixed. But I don't think
it's a good idea to _just_ remove that 'else' since its does work for
codec-dai. Instead, I think you might need to check the set_sysclk()
of cpu-dai driver as I mentioned in the last mail:

 The sysclk direction is only valid when indicating MCLK as sysclk
 (FSYNC or BCLK shall follow CBS_CFS/CBM_CFM setting).So basically
 if cpu-dai driver gets sysclk configuration with SND_SOC_CLOCK_IN,
 shouldn't it just set the internal direction for MCLK's PAD and
 return the call directly? (I'm guessing there also might be some
 tiny work for your cpu-dai driver to enhance the validation part.)

Best regards,
Nicolin