linux-kernel - Re: [RFC PATCH] ASoC: wm8731: let codec to manage clock by itself

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Message-ID: <20150203162128.GP21293@sirena.org.uk>
Date:	Tue, 3 Feb 2015 16:21:28 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Manuel Lauss <manuel.lauss@...il.com>
Cc:	Bo Shen <voice.shen@...el.com>,
	Manuel Lauss <manuel.lauss@...glemail.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>,
	Richard Purdie <richard@...nedhand.com>,
	patches@...nsource.wolfsonmicro.com, linux-sound@...r.kernel.org,
	alsa-devel <alsa-devel@...a-project.org>,
	linux-arm-kernel@...ts.infradead.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] ASoC: wm8731: let codec to manage clock by itself

On Tue, Feb 03, 2015 at 03:40:45PM +0100, Manuel Lauss wrote:
> On Tue, Feb 3, 2015 at 1:44 PM, Mark Brown <broonie@...nel.org> wrote:

> >> +    wm8731->mclk = devm_clk_get(&spi->dev, "mclk");
> >> +    if (IS_ERR(wm8731->mclk)) {
> >> +        wm8731->mclk = NULL;
> >> +        dev_warn(&spi->dev, "assuming static MCLK\n");
> >> +    }

> > This is broken for both deferred probe and in the case where the clock
> > API genuinely returns a NULL clock.  Other than that it's the kind of
> > thing that we've done for some other drivers, though it's not good to
> > have to do this.  Check them for correct behaviour.

> Hm, so the only option is to create the simples possible 12MHz clk object?

Well, that's the best option in general.  You can get away with just
making sure that -EPROBE_DEFER is handled and that IS_ERR() is used to
check for an invalid clock but if you can define a clock that's even
better (and should be pretty painless), we're going to want to do that
transition at some point.

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