[alsa-devel] Disable DAPM for click avoidance ?

[Mark Brown]

On Thu, Nov 23, 2017 at 03:32:26PM +0100, Ricard Wanderlof wrote:
> On Thu, 23 Nov 2017, Mark Brown wrote:

> > Yes, you'll need to do something like leave the outputs enabled.  Most
> > devices have some facility to keep VMID switched to the outputs, though
> > I did see a few where someone thought it was a good idea to power on
> > from cold always.  A device that old isn't going to be that competitive
> > power wise anyway even if it were well implemented which this one seems
> > to not have been.

> In my case the codec is only a couple of years old, so I'd say it 
> qualifies as 'modern'. There's a table in the data sheet describing the 

Wow, people are still designing new VMID based CODECs - what is this one?

> > That's what the digital mute handling is for - we're just throwing away
> > any garbage the CPU puts out before it's stable.  We're not expecting it
> > to work around any CODEC side issues.

> During which time period is the digital mute enabled? From the first 
> stream startup until everything is up and running?

It should be enabled at all times that we're not actively playing
anything.  Though now that I think about it we need to go through and
mute everything during probe otherwise it won't be muted on first power
on.

> > If you're getting L/R swap issues on some startups leaving things
> > enabled all the time will mean that your random swap issue gets moved to
> > boot.

> Basically the situation I had was that it worked fine on first startup, it 
> was on subsequent startups/shutdowns that the problems occurred, as
> shutting down the audio streams seemed to leave the CPU DAI in some 
> intermediate state, from which it could only recover if completely reset, 
> which did not play well with the concept of for instance having a capture 
> stream running continuously while a playback stream was started and 
> stopped.

That's a new (and buggy) one...
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