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From: Mark Brown <broonie@kernel.org>
To: Richard Genoud <richard.genoud@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Bo Shen <voice.shen@atmel.com>,
	Lars-Peter Clausen <lars@metafoo.de>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org,
	devicetree-discuss@lists.ozlabs.org
Subject: Re: [PATCH v5 1/7] sound: codec: wm8731: add rates constraints
Date: Mon, 15 Jul 2013 16:22:28 +0100	[thread overview]
Message-ID: <20130715152228.GJ11538@sirena.org.uk> (raw)
In-Reply-To: <CACQ1gAhmp-i7vzPKuTMxqs9Ytjynz9NTvrQk9R08U9Fo-cVzMg@mail.gmail.com>

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On Mon, Jul 15, 2013 at 04:53:46PM +0200, Richard Genoud wrote:
> 2013/7/12 Mark Brown <broonie@kernel.org>:

> > This isn't going to work with systems which have a variable clock as the
> > input to the CODEC.  If it's imposing constraints the driver needs to
> > allow setting the clock to zero as a way of removing constraints (and
> > any existing drivers should be updated to do this if needed).

> Maybe I'm wrong, but I didn't find any system using variable clock
> with this codec.

The driver should be written with that possibility in mind even if there
were no users; it only takes a couple of lines of code.

> The sam9g20ek (soc/atmel/sam9g20_wm8731.c) is not using a crystal, but
> it's using a fixed clock anyway.
> But there's soc/pxa/corgi.c and soc/pxa/poodle.c that puzzle me.
> They seems to use a crystal, but they are setting a different sysclk
> depending on the rate.
> That seems wrong, but as I'm a newbie in ASoC...

Note that the CPU is clock master for those - it's going to be
outputting a clock based on the sample rate selected automatically.
These boards would be broken by your change as it stands.

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WARNING: multiple messages have this Message-ID (diff)
From: broonie@kernel.org (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 1/7] sound: codec: wm8731: add rates constraints
Date: Mon, 15 Jul 2013 16:22:28 +0100	[thread overview]
Message-ID: <20130715152228.GJ11538@sirena.org.uk> (raw)
In-Reply-To: <CACQ1gAhmp-i7vzPKuTMxqs9Ytjynz9NTvrQk9R08U9Fo-cVzMg@mail.gmail.com>

On Mon, Jul 15, 2013 at 04:53:46PM +0200, Richard Genoud wrote:
> 2013/7/12 Mark Brown <broonie@kernel.org>:

> > This isn't going to work with systems which have a variable clock as the
> > input to the CODEC.  If it's imposing constraints the driver needs to
> > allow setting the clock to zero as a way of removing constraints (and
> > any existing drivers should be updated to do this if needed).

> Maybe I'm wrong, but I didn't find any system using variable clock
> with this codec.

The driver should be written with that possibility in mind even if there
were no users; it only takes a couple of lines of code.

> The sam9g20ek (soc/atmel/sam9g20_wm8731.c) is not using a crystal, but
> it's using a fixed clock anyway.
> But there's soc/pxa/corgi.c and soc/pxa/poodle.c that puzzle me.
> They seems to use a crystal, but they are setting a different sysclk
> depending on the rate.
> That seems wrong, but as I'm a newbie in ASoC...

Note that the CPU is clock master for those - it's going to be
outputting a clock based on the sample rate selected automatically.
These boards would be broken by your change as it stands.
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  reply	other threads:[~2013-07-15 15:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-11 16:15 [PATCH v5 0/7] Sound support for at91sam9x5-wm8731 based boards Richard Genoud
2013-07-11 16:15 ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 1/7] sound: codec: wm8731: add rates constraints Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-12 11:45   ` Mark Brown
2013-07-12 11:45     ` Mark Brown
2013-07-12 11:45     ` Mark Brown
2013-07-15 14:53     ` Richard Genoud
2013-07-15 14:53       ` Richard Genoud
2013-07-15 15:22       ` Mark Brown [this message]
2013-07-15 15:22         ` Mark Brown
2013-07-11 16:15 ` [PATCH v5 2/7] sound: sam9x5_wm8731: machine driver for at91sam9x5 wm8731 boards Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-12 11:49   ` Mark Brown
2013-07-12 11:49     ` Mark Brown
2013-07-12 11:49     ` Mark Brown
2013-07-15 14:59     ` Richard Genoud
2013-07-15 14:59       ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 3/7] Documentation: DT: update atmel SSC with DMA binding Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 4/7] ARM: AT91: DTS: sam9x5: add SSC DMA parameters Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 5/7] ARM: AT91: DTS: sam9x5ek: add WM8731 codec Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 6/7] ARM: AT91: DTS: sam9x5ek: enable SSC Richard Genoud
2013-07-11 16:15   ` Richard Genoud
2013-07-11 16:15 ` [PATCH v5 7/7] ARM: AT91: DTS: sam9x5ek: add sound configuration Richard Genoud
2013-07-11 16:15   ` Richard Genoud

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