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

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Message-ID: <20210311161558.GG4962@sirena.org.uk>
Date:   Thu, 11 Mar 2021 16:15:58 +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 Wed, Mar 10, 2021 at 08:20:28PM +0530, Sameer Pujar wrote:

> If I read this correctly below is the configuration you need,
> SoC -> MCLK(fixed rate) -> PLL(wm8904) -> PLL output (256 * fs) -> sysclk

For this device for integration with something like simple-audio-card
since there's limited flexibility within the device the simplest thing
would be to not make the internal clocking of the device visible and
just have it figure out how to use the input clock, using the MCLK
directly if possible otherwise using the FLL to generate a suitable
clock.  The trick is figuring out if it's best to vary the input clock
or to use the FLL to adapt a fixed input clock, and of course adapting
any existing users if things get changed.

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