RE: Re: Re: [PATCH 4/4] ASoC: wm8524: Delay some time to follow power up sequency

[Chancel Liu]

> > > On Wed, Feb 22, 2023 at 07:39:45PM +0800, Chancel Liu wrote:
> > > Doing a 100ms busy wait in atomic context does not seem like a great
> > > idea, never mind a 1.5s one.  This shouldn't be done in trigger, it
> > > needs to be done later - digital_mute() might be a better time to hook
> > > in, though longer delays like this are really quite bad.
>
> > Yes, such long time delay in driver is very bad. But this device requires
> > waiting some time before able to output audio. We have to wait otherwise
> > the beginning data may be lost.
>
> It's not just that it's doing this in the driver, it's doing it in the
> trigger() function which runs in atomic context.  That's unreasonable.
>
> > The power up to audio out timing occurs after MCLK, BCLK and MUTE=1 are
> > ready. I added the delay in trigger() because some CPU DAI drivers enable BCLK in
> > trigger(). You suggested moving the delay to digital_mute(). It seems
> > digital_mute() is called before cpu_dai->trigger. Please correct me if I'm
> > wrong.
> 
> Hrm, right - in any case, it needs to be somewhere that isn't atomic
> context.

OK. I will keep PATCH 1 and PATCH 3. 

For PATCH 2 and PATCH 4, I have to find a better way in which long time delay
can be avoided in atomic context.

Thank you very much for your comments.

Regards, 
Chancel Liu