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

Lukasz Majewski
2022-12-15T08:54:24Z

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Hi Mark,

> 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.
>

This patch steamed from 4.4 Linux. On the newer Linux version the
"distortion" problem is not present anymore.

I will drop this patch.

> > 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
>
> --
>
> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma@denx.de

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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