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

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Date:	Wed, 4 Feb 2015 11:45:29 +0800
From:	Bo Shen <voice.shen@...el.com>
To:	Mark Brown <broonie@...nel.org>,
	Manuel Lauss <manuel.lauss@...il.com>
CC:	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

Hi Mark,

On 02/04/2015 12:21 AM, Mark Brown wrote:
> 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.

Do you mean I send my RFC patch as the formal patch, and let other 
boards which use the wm8731 to add clk object, am I right?

Best Regards,
Bo Shen

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