linux-kernel - RE: [PATCH] spi/atmel: add support for runtime PM

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Date:	Tue, 21 Oct 2014 00:51:20 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Kevin Hilman <khilman@...nel.org>
CC:	Mark Brown <broonie@...nel.org>,
	"linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH] spi/atmel: add support for runtime PM

Hi Kevin,

> -----Original Message-----
> From: Kevin Hilman [mailto:khilman@...nel.org]
> Sent: Tuesday, October 21, 2014 2:09 AM
> To: Yang, Wenyou
> Cc: Mark Brown; linux-spi@...r.kernel.org; linux-kernel@...r.kernel.org; Ferre,
> Nicolas; linux-arm-kernel@...ts.infradead.org
> Subject: Re: [PATCH] spi/atmel: add support for runtime PM
> 
> "Yang, Wenyou" <Wenyou.Yang@...el.com> writes:
> 
> >> -----Original Message-----
> >> From: Kevin Hilman [mailto:khilman@...nel.org]
> >> Sent: Friday, October 17, 2014 10:22 PM
> >> To: Mark Brown
> >> Cc: Yang, Wenyou; linux-spi@...r.kernel.org;
> >> linux-kernel@...r.kernel.org; Ferre, Nicolas;
> >> linux-arm-kernel@...ts.infradead.org
> >> Subject: Re: [PATCH] spi/atmel: add support for runtime PM
> >>
> >> Mark Brown <broonie@...nel.org> writes:
> >>
> >> > On Fri, Oct 17, 2014 at 06:02:35AM -0700, Kevin Hilman wrote:
> >> >> Wenyou Yang <wenyou.yang@...el.com> writes:
> >> >
> >> >> > +	if (!pm_runtime_suspended(dev)) {
> >> >> > +		clk_disable_unprepare(as->clk);
> >> >> > +		pinctrl_pm_select_sleep_state(dev);
> >> >> > +	}
> >> >
> >> >> a.k.a. pm_runtime_put_sync() since the ->runtime_suspend()
> >> >> callback does the same thing.
> >> >
> >> > Will that do the right thing when runtime PM is disabled in Kconfig?
> >>
> >> Good point.
> >>
> >> Then the way to make this cleaner, and obvious on inspection that
> >> system suspend/resume are doing the same thing as runtime
> >> suspend/resume is to have -
> >> >suspend call the runtime_suspend function.
> >>
> >> The runtime suspend/resume functions then should be wrapped in
> >> CONFIG_PM instead of CONFIG_PM_RUNTIME.
> > But if the runtime PM is disabled, __pm_runtime_idle() return -ENOSYS,
> > which invoked by pm_runtime_put_sync(), in spite of the runtime
> > suspend/resume functions wrapper,
> 
> You won't be calling _put_sync(), instead you'll just directly call
> atmel_spi_runtime_suspend().
Got it , I will change it. Thanks.

> 
> The goal is to make it obvious upon reading that ->suspend and
> ->runtime_suspend are doing exactly the same thing.
> 
> Kevin

Best Regards,
Wenyou Yang
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