linux-kernel - Re: [PATCH] ASoC: fsl_spdif: don't change the root clock rate of spdif in driver

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Message-ID: <20140917013251.GA4796@dragon>
Date:	Wed, 17 Sep 2014 09:32:52 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Nicolin Chen <nicoleotsuka@...il.com>
CC:	Shengjiu Wang <shengjiu.wang@...escale.com>, <timur@...i.org>,
	<Li.Xiubo@...escale.com>, <lgirdwood@...il.com>,
	<broonie@...nel.org>, <perex@...ex.cz>, <tiwai@...e.de>,
	<alsa-devel@...a-project.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: fsl_spdif: don't change the root clock rate of
 spdif in driver

On Tue, Sep 16, 2014 at 11:19:28AM -0700, Nicolin Chen wrote:
> On Tue, Sep 16, 2014 at 07:46:34PM +0800, Shengjiu Wang wrote:
> > The spdif root clock may be used by other module or defined with
> > CLK_SET_RATE_GATE, so we can't change the clock rate in driver.
> > In this patch remove the clk_set_rate and clk_round_rate to protect the
> > clock.
> 
> It's a quite convenient and conservative way to remove the clock
> dealing code in the driver, however, it may result less flexible
> functionalities.
> 
> The reason why I left the clk_set_rate() in the driver is to hope
> we may find a better way to tackle those tough situations. For IP
> itself, it doesn't matter if the clock the SoC provides to it is
> being shared by other modules or not.
> 
> So I think, if it's a shared clock, we should not define it as a
> rate-changeable one in the SoC level, as we might still have some
> SoCs provide a dedicated clock to S/PDIF so as to get the maximum
> range of clock support for users.
> 
> @Shawn
> Sorry to involve you in this topic. I'm not so sure if we can do
> this in the clock driver so that the clock rate would be fixed
> even if the driver is trying to change it. If we can, I think we
> may use a better solution here instead.

No, we do not have anything like that today.

Shawn
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