linux-kernel - Re: [alsa-devel] [PATCH 1/2 v2] ASoC: sh: fsi: Add runtime PM support

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Date:	Mon, 9 Nov 2009 13:31:36 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Kuninori Morimoto <morimoto.kuninori@...esas.com>
Cc:	alsa-devel@...a-project.org, Magnus Damm <damm@...nsource.se>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [alsa-devel] [PATCH 1/2 v2] ASoC: sh: fsi: Add runtime PM
	support

On Mon, Nov 09, 2009 at 10:58:58AM +0000, Mark Brown wrote:

Adding in an address for Magnus which hopefully won't bounce and also
the linux-pm list which get_maintainers didn't find.

> On Mon, Nov 09, 2009 at 11:54:47AM +0900, Kuninori Morimoto wrote:
> > This patch add support runtime PM.
> > Driver callbacks for Runtime PM are empty because
> > the device registers are always re-initialized after
> > pm_runtime_get_sync(). The Runtime PM functions replaces the
> > clock framework module stop bit handling in this driver.
> 
> > Signed-off-by: Kuninori Morimoto <morimoto.kuninori@...esas.com>
> 
> Hrm.  I'll have to see how this plays with ASoC core pm_runtime support
> when that appears.  It should be OK as-is, I think.
> 
> > +	pm_suspend_ignore_children(&pdev->dev, true);
> > +	pm_runtime_enable(&pdev->dev);
> > +	pm_runtime_resume(&pdev->dev);
> 
> Why pm_suspend_ignore_all_children()?  I'd not expect the device to have
> any children and if it did it doesn't seem like an entirely safe
> assumption.
> 
> > +static int fsi_runtime_nop(struct device *dev)
> > +{
> > +	/* Runtime PM callback shared between ->runtime_suspend()
> > +	 * and ->runtime_resume(). Simply returns success.
> > +	 *
> > +	 * This driver re-initializes all registers after
> > +	 * pm_runtime_get_sync() anyway so there is no need
> > +	 * to save and restore registers here.
> > +	 */
> > +	return 0;
> > +}
> 
> This sets off alarm bells but it's perfectly reasonable, especially with
> platforms able to put things into a low power state with no explicit
> driver code now they can do power domain style things like SH.  I've
> CCed in the PM folks since this seems like a perfectly reasonable use
> case which ought to be handled more nicely.
> --
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