linux-kernel - Re: [PATCH 3/3] ASoC: wm8940: Mute also the speaker output

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Date:   Mon, 6 Jun 2022 17:25:19 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Lukasz Majewski <lukma@...x.de>
Cc:     Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com, alsa-devel@...a-project.org,
        Takashi Iwai <tiwai@...e.com>, Jaroslav Kysela <perex@...ex.cz>
Subject: Re: [PATCH 3/3] ASoC: wm8940: Mute also the speaker output

On Mon, Jun 06, 2022 at 05:44:41PM +0200, Lukasz Majewski wrote:

> Without this change the BTL speaker produces some
> "distortion" noise when test program
> (speaker-test -t waw) is ended with ctrl+c.

> As our design uses speaker outputs to drive BTL speaker,
> it was necessary to also mute the speaker via the codec
> internal WM8940_SPKVOL register with setting
> WM8940_SPKMUTE bit.

This will not interact well with both the user visible control of the
speaker volume via the Speaker Playback Volume control and the analog
bypass paths that the device has - it'll change the state of the control
without generating any events, and cut off any bypassed audio that's
mixed in.

You can probably achieve a similar effect by making the control an
_AUTODISABLE one which will allow the core to mute the control when it's
not being used in a way that's not visible to userspace.

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