linux-kernel - Re: [PATCH 3/4] ASoC: wm8940: Mute also the speaker output

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Date:   Wed, 14 Dec 2022 13:09:12 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Lukasz Majewski <lukma@...x.de>
CC:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Stephen Kitt <steve@....org>,
        <patches@...nsource.cirrus.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] ASoC: wm8940: Mute also the speaker output

On Wed, Dec 14, 2022 at 01:37:42PM +0100, 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.
> 
> Signed-off-by: Lukasz Majewski <lukma@...x.de>
> ---
> +	spkvol_reg &= ~WM8940_SPKMUTE;
> +	if (mute) {
>  		mute_reg |= 0x40;
> +		spkvol_reg |= WM8940_SPKMUTE;
> +	}
> +
> +	ret = snd_soc_component_write(component, WM8940_SPKVOL, spkvol_reg);
> +	if (ret)
> +		return ret;

This bit is also controlled by the "Speaker Playback Switch" so
you probably need some locking between them to stop them
clobbering each other.

Thanks,
Charles