linux-kernel - Re: [PATCH 2/3] ASoC: tlv320aic3x: use BCLK instead of MCLK if not in master mode

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Date:   Wed, 5 Jul 2023 21:56:11 +0200
From:   Andreas Kemnade <andreas@...nade.info>
To:     Mark Brown <broonie@...nel.org>
Cc:     bcousson@...libre.com, tony@...mide.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        lgirdwood@...il.com, perex@...ex.cz, tiwai@...e.com,
        peter.ujfalusi@...il.com, jarkko.nikula@...mer.com,
        dmitry.torokhov@...il.com, linux-omap@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH 2/3] ASoC: tlv320aic3x: use BCLK instead of MCLK if not
 in master mode

On Wed, 5 Jul 2023 20:21:58 +0100
Mark Brown <broonie@...nel.org> wrote:

> On Wed, Jul 05, 2023 at 09:03:23PM +0200, Andreas Kemnade wrote:
> 
> > +	/* probably no mclk if not master, so rely on bitclk */
> > +	if (!aic3x->master)
> > +		clk_id = 2;
> > +  
> 
> This is fairly clearly a massive hack, we're just silently ignoring the
> clock we were asked to configure and choosing another one which is
> likely at a different rate to that we were expecting and sadly the
> driver didn't provide an automatic mode due to how old it is.  We also
> appear to try to use the configured clock rate during PLL setup which
> still happens in hw_params() even with this change which is a bit of a
> concern here.  Are you sure hw_params ends up doing the right thing, and
> that there are no other systems that get broken by this (perhaps ones
> sending a lower BCLK for example)?

Yes, I am not that happy myself with that one. Possible victim is
keystone-k2g-evm.dts. 
I looked for if (master) things and found the pll enable/disable connected to it.
But that is not the whole story...
> 
> It would be nicer to set the clock via the DT bindings, ideally with the
> clock bindings...

I found no path from these simple-audio-card things to provide a clk_id 
to set_dai_sysclk. I would of course prefer such a thing. Do I have overlooked
something?

Regards,
Andreas