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

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Message-ID: <20221214215546.657a04f3@wsk>
Date:   Wed, 14 Dec 2022 21:55:46 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Charles Keepax <ckeepax@...nsource.cirrus.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

Hi Mark,

> 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.  
> 
> > @@ -465,9 +465,18 @@ static int wm8940_mute(struct snd_soc_dai
> > *dai, int mute, int direction) {  
> 
> > +	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;
> >  
> >  	return snd_soc_component_write(component, WM8940_DAC,
> > mute_reg);  
> 
> In addition to the issue Charles raised this is simply not what the
> mute callback should do, the mute callback should specifically mute
> the digital input (with the goal of masking any glitching on there
> while clocks are started/stopped). 

Ok

> Looking at the driver the device
> supports analogue bypass paths to the speaker - these will be broken
> by your patch

I was not aware about this side effect. I just wanted to be sure that
the speaker is muted.

> so if you genuinely need some workaround in this area
> I'd be looking at the Speaker Mixer PCM Playback Switch rather than
> muting the speaker as a whole.

I would be more than happy if I could use for example the 'amixer'
command to setup the audio correctly without this patch. 

For example - on this system - before I run any speaker test I need to
call: amixer -d set 'Speaker Mixer PCM',0 on

to unmute the system.

>  If the device just can't cope without
> an input then ignore_mdown_time might be what you're looking for, it
> looks like the device doesn't have any lengthy sleeps in the power
> up/down paths so that should be fine so long as it doesn't pop/click.
> 

Ok. I will check this as well.

> I'd also check there's not some other system configuration issue here
> which is more obvious when the input from the DAC stops getting input,
> check that you don't see similar issues when silence is played for
> example.  It might be worth checking that none of the analogue bypass
> paths are enabled.

Thanks for your hints. I will investigate it further.

It looks like this patch is some kind of a hack, to fix my system
configuration and shall be dropped in v2.


Best regards,

Lukasz Majewski

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