linux-kernel - Re: [PATCH] ASoC: max98357a: Add mixer control to mute/unmute speaker

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Message-ID: <Ybs/i3Lg9VN0d4kg@sirena.org.uk>
Date:   Thu, 16 Dec 2021 13:30:51 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Ajit Kumar Pandey <AjitKumar.Pandey@....com>
Cc:     alsa-devel@...a-project.org, Vijendar.Mukunda@....com,
        Alexander.Deucher@....com, Basavaraj.Hiregoudar@....com,
        Sunil-kumar.Dommati@....com, Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: max98357a: Add mixer control to mute/unmute speaker

On Thu, Dec 16, 2021 at 05:54:45PM +0530, Ajit Kumar Pandey wrote:

> Thanks for suggestion. We tried using SND_SOC_DAPM_PIN_SWITCH() for the
> speaker widget and it invoke dapm_event callback based on switch i.e
> max98357a_sdmode_event() but codec driver isn't enabling/disabling gpios in
> such event callback instead they are doing that in dai_ops trigger callback.
> In our platform single I2S controller instance (cpu-dai) is connected to two
> different endpoints with a single PCM device, hence we want to switch or
> enable/disable output based on Machine driver controls only.

DAPM should cope perfectly fine with this setup...

> Initially we thought to configure gpio within sdmode_event callback but
> there was some pop noise issue reported in one platform with that change
> hence reverted. Check https://patchwork.kernel.org/project/alsa-devel/patch/20200721114232.2812254-1-tzungbi@google.com/#23502085
> So we thought of exposing a mixer control to enable/disable amp from UCM
> in our platform without breaking existing functionality. Please let us
> know any other alternative way if possible.

Whatever is going on this should be managed from the driver rather than
having a direct control, especially given the issues I mentioned with
there being zero coordination between this and the management that the
driver already does.  You could have DAPM controls set a variable and
coordinate with whatever you're doing in the pcm_ops, I'm not clear what
the use case is for having the manual control TBH.

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