linux-kernel - Re: [PATCH V3 1/2] clk: imx6: Add SPDIF

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Date:	Mon, 19 Oct 2015 23:36:18 +0800
From:	Shawn Guo <shawnguo@...nel.org>
To:	Michael Turquette <mturquette@...libre.com>
Cc:	Shengjiu Wang <shengjiu.wang@...escale.com>, kernel@...gutronix.de,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux@....linux.org.uk, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/2] clk: imx6: Add SPDIF_GCLK clock in clock tree

Hi Mike,

On Mon, Oct 19, 2015 at 08:28:07AM -0700, Michael Turquette wrote:
> Quoting Shengjiu Wang (2015-10-10 03:15:06)
> > Correct SPDIF clock setting issue in clock tree, the SPDIF_GCLK is also
> > one clock of SPDIF, which is missed before.
> > 
> > We found an issue that imx can't enter low power mode with spdif
> > if IMX6x_CLK_SPDIF is used as the core clock of spdif. Because
> > spdif driver will register IMX6x_CLK_SPDIF clock to regmap, regmap will do
> > clk_prepare in init function, then IMX6x_CLK_SPDIF clock is prepared in probe,
> > so its parent clock (PLL clock) is prepared, the prepare operation of
> > PLL clock is to enable the clock. But I.MX needs all PLL clock is disabled,
> > then it can enter low power mode.
> > 
> > So we can't use IMX6x_CLK_SPDIF as the core clock of spdif, the correct spdif
> > core clock is SPDIF_GCLK, which share same gate bit with IMX6x_CLK_SPDIF clock.
> > SPDIF_GCLK's parent clock is ipg clock.
> 
> I'm confused by this. Is there really a new clock signal to be added, or
> this just to workaround some reference counting problems with regmap?

I was confused by the previous version of the patch, and asked Shengjiu
to improve the commit log, which seems still not so good.  In short, the
patch does add a missing clock, and the missing of the clock is
discovered by a low-power-mode issue when SPDIF driver is enabled.

> 
> > 
> > Signed-off-by: Shengjiu Wang <shengjiu.wang@...escale.com>
> 
> Please Cc the linux-clk@...r.kernel.org mailing list for future clock
> driver patches.

Right, should have reminded him.  I will keep my eyes more closely on
this.

Shawn
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