From:   Chancel Liu <chancel.liu@nxp.com>
To:     Mark Brown <broonie@kernel.org>
CC:     "lgirdwood@gmail.com" <lgirdwood@gmail.com>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "krzysztof.kozlowski+dt@linaro.org" 
        <krzysztof.kozlowski+dt@linaro.org>,
        "perex@perex.cz" <perex@perex.cz>,
        "tiwai@suse.com" <tiwai@suse.com>,
        "ckeepax@opensource.cirrus.com" <ckeepax@opensource.cirrus.com>,
        "patches@opensource.cirrus.com" <patches@opensource.cirrus.com>,
        "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>
Subject: RE: Re: Re: [PATCH 4/4] ASoC: wm8524: Delay some time to follow power
 up sequency
Thread-Topic: Re: Re: [PATCH 4/4] ASoC: wm8524: Delay some time to follow
 power up sequency
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Date:   Mon, 27 Feb 2023 09:07:06 +0000
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> > > 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 hoo=
k
> > > in, though longer delays like this are really quite bad.
>
> > Yes, such long time delay in driver is very bad. But this device requir=
es
> > waiting some time before able to output audio. We have to wait otherwis=
e
> > 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=3D1 a=
re
> > ready. I added the delay in trigger() because some CPU DAI drivers enab=
le 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.
>=20
> Hrm, right - in any case, it needs to be somewhere that isn't atomic
> context.

OK. I will keep PATCH 1 and PATCH 3.=20

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

Thank you very much for your comments.

Regards,=20
Chancel Liu