linux-kernel - Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock

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Message-ID: <20210315153925.GC4595@sirena.org.uk>
Date:   Mon, 15 Mar 2021 15:39:25 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Sameer Pujar <spujar@...dia.com>
Cc:     Michael Walle <michael@...le.cc>, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, jonathanh@...dia.com,
        kuninori.morimoto.gx@...esas.com, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, robh@...nel.org, sharadg@...dia.com,
        thierry.reding@...il.com
Subject: Re: [PATCH 1/3] ASoC: simple-card-utils: Fix device module clock

On Mon, Mar 15, 2021 at 08:49:00PM +0530, Sameer Pujar wrote:
> On 3/15/2021 5:35 PM, Michael Walle wrote:
> > Am 2021-03-12 14:46, schrieb Mark Brown:

> > Sameer, it looks like the proper fix should be to add the clock
> > support to your codec.

> I agree that complicated clock relationships should be handled within the
> codec itself, however MCLK rate setting depends on "mclk-fs" factor and this
> property is specified as part of simple-card/audio-graph-card codec subnode.
> Right now codec, in general, does not have a way to know this. The
> set_sysclk() callback takes rate argument and not the factor. Moreover the

I just don't understand what you're saying here at all.  At the point
where the card is setting the clock API clock rate it can just as well
set a sysclk, these are equivalent operations.

> same codec is used by other platform vendors too and unless a new DT
> property is added for codec, runtime MCLK update based on the scaling factor
> cannot be supported. This would mean that we will be having two methods to
> specify "mclk-fs" factor, one from simple-card/audio-graph-card and one from
> respective codec nodes, which does not seem ideal.

Again I just can't follow what you're saying here at all.  Again, if the
card is able to set a clock API clock rate it can just as well set a
clock rate via sysclk.

> Yes this is a problem, unfortunately I missed checking some of the
> simple-card examples. I wonder we should be specifically looking for "mclk"
> clock here.

That would definitely help mitigate the problem but I really think it's
cleaner and safer to just push this down to set_sysclk().

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