Re: [RFC PATCH] ASoC: wm_adsp: Change ADSPs to be mixer widgets rather the PGAs

[Charles Keepax <ckeepax@opensource.wolfsonmicro.com>]

On Wed, Dec 18, 2013 at 11:27:39AM +0000, Mark Brown wrote:
> On Wed, Dec 18, 2013 at 10:53:44AM +0000, Charles Keepax wrote:
> 
> > Was also considering if it would be worth adding an
> > additional snd_soc_dapm_dsp id? That could sit between
> > mixers and pgas, but I can't really see any obvious issue
> > with treating the DSP as a mixer and it is a much simpler
> > change. Although I am open to writing the other change if it
> > is preferred?
> 
> One of the issues here was trying to ensure that the DSP started up with
> its inputs stable so noise from them starting didn't propagage into the
> algorithm and confuse it.  The expecation with putting it as a PGA was
> that it would start with the outputs mute and do a digital unmute to
> bring them up.  Since everything is digital this should all be more
> robust than it would be for analogue.

Muting the output is a little tricky though as a graph walk will
be required to determine which output was connected, unless you
have any handy ideas I have not spotted? I will start having a
look to see what could be done on the muting front.

Thanks,
Charles