linux-kernel - Re: [PATCH v3 4/5] ASoC: codecs: lpass-wsa-macro: fix compander volume hack

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Message-ID: <ZaouZXdxWv3oahDl@hovoldconsulting.com>
Date: Fri, 19 Jan 2024 09:10:13 +0100
From: Johan Hovold <johan@...nel.org>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc: Johan Hovold <johan+linaro@...nel.org>, Mark Brown <broonie@...nel.org>,
	Banajit Goswami <bgoswami@...cinc.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
	alsa-devel@...a-project.org, linux-sound@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v3 4/5] ASoC: codecs: lpass-wsa-macro: fix compander
 volume hack

On Fri, Jan 19, 2024 at 07:45:45AM +0000, Srinivas Kandagatla wrote:
> On 18/01/2024 16:58, Johan Hovold wrote:
> > The LPASS WSA macro codec driver is updating the digital gain settings
> > behind the back of user space on DAPM events if companding has been
> > enabled.
> > 
> > As compander control is exported to user space, this can result in the
> > digital gain setting being incremented (or decremented) every time the
> > sound server is started and the codec suspended depending on what the
> > UCM configuration looks like.
> > 
> > Soon enough playback will become distorted (or too quiet).
> > 
> > This is specifically a problem on the Lenovo ThinkPad X13s as this
> > bypasses the limit for the digital gain setting that has been set by the
> > machine driver.
> > 
> > Fix this by simply dropping the compander gain offset hack. If someone
> > cares about modelling the impact of the compander setting this can
> > possibly be done by exporting it as a volume control later.
> > 
> > Note that the volume registers still need to be written after enabling
> > clocks in order for any prior updates to take effect.
> > 
> > Fixes: 2c4066e5d428 ("ASoC: codecs: lpass-wsa-macro: add dapm widgets and route")
> > Cc: stable@...r.kernel.org      # 5.11
> > Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > ---
> >   sound/soc/codecs/lpass-wsa-macro.c | 7 -------
> >   1 file changed, 7 deletions(-)
> > 
> > diff --git a/sound/soc/codecs/lpass-wsa-macro.c b/sound/soc/codecs/lpass-wsa-macro.c
> > index 7e21cec3c2fb..6ce309980cd1 100644
> > --- a/sound/soc/codecs/lpass-wsa-macro.c
> > +++ b/sound/soc/codecs/lpass-wsa-macro.c
> > @@ -1584,7 +1584,6 @@ static int wsa_macro_enable_interpolator(struct snd_soc_dapm_widget *w,
> >   	u16 gain_reg;
> >   	u16 reg;
> >   	int val;
> > -	int offset_val = 0;
> 
> TBH, as discussed in my previous review we should just remove 
> spkr_gain_offset and associated code path.

I don't understand what you are referring to. Are you talking about the
"ear_spkr_gain" perhaps?

I left that hack in place for now, as it's not currently an issue. It
could perhaps be removed later.

Johan