linux-kernel - Re: [PATCH 04/12] ASoC: cs42l42: Don't reconfigure the PLL while it is running

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Message-ID: <20210811115637.GA4167@sirena.org.uk>
Date:   Wed, 11 Aug 2021 12:56:37 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     alsa-devel@...a-project.org, patches@...nsource.cirrus.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] ASoC: cs42l42: Don't reconfigure the PLL while it
 is running

On Tue, Aug 10, 2021 at 05:27:45PM +0100, Richard Fitzgerald wrote:
> On 10/08/2021 16:49, Mark Brown wrote:

> > Shouldn't the PLL code be noticing problematic attempts to reconfigure
> > the PLL while it's active rather than the individual callers?

> It's wrong for a hw_params() for one stream to try to configure the PLL
> when the other stream has already called hw_params(), configured the PLL
> and started it. E.g. if you started a PLAYBACK, configured and
> started everything, then got another hw_params() for the CAPTURE.

> cs42l42_pll_config() could check whether it is already running and skip
> configuration in that case, but that seems to me a rather opaque
> implementation. In my opinion this doesn't really fall into the case of
> ignoring-bad-stuff-to-be-helpful (like free() accepting a NULL).

This doesn't treat the situation as an error though, it just ignores it,
and there's nothing to stop _pll_config() generating a warning if that
makes sense.

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