Re: [PATCH v8 1/5] PM / Runtime: Add getter for querying the IRQ safe option

From: Pavel Machek <pavel@ucw.cz>
To: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <len.brown@intel.com>, Jonathan Corbet <corbet@lwn.net>,
	Russell King <linux@arm.linux.org.uk>,
	Dan Williams <dan.j.williams@intel.com>,
	Vinod Koul <vinod.koul@intel.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	linux-pm@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
	Lars-Peter Clausen <lars@metafoo.de>,
	Michal Simek <michal.simek@xilinx.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v8 1/5] PM / Runtime: Add getter for querying the IRQ safe option
Date: Fri, 31 Oct 2014 15:22:41 +0100	[thread overview]
Message-ID: <20141031142241.GA17547@amd> (raw)
In-Reply-To: <1414746895.6797.3.camel@AMDC1943>

On Fri 2014-10-31 10:14:55, Krzysztof Kozlowski wrote:
> On pon, 2014-10-20 at 11:04 +0200, Krzysztof Kozlowski wrote:
> > Add a simple getter pm_runtime_is_irq_safe() for querying whether runtime
> > PM IRQ safe was set or not.
> > 
> > Various bus drivers implementing runtime PM may use choose to suspend
> > differently based on IRQ safeness status of child driver (e.g. do not
> > unprepare the clock if IRQ safe is not set).
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
> 
> Rafael, Len, Pavel,
> 
> Is proposed API ok? Do you have any comments?
> 
> I'll upload whole patchset to Russell's patch tracking system. However
> an ack from PM maintainer is probably needed.

I don't like the API. Having callbacks work in different context (irq
/ noirq) based on what another function reports is ugly.

What is the penalty if we always decide callbacks are not IRQ safe?
								Pavel

> > --- a/Documentation/power/runtime_pm.txt
> > +++ b/Documentation/power/runtime_pm.txt
> > @@ -468,6 +468,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
> >      - set the power.irq_safe flag for the device, causing the runtime-PM
> >        callbacks to be invoked with interrupts off
> >  
> > +  bool pm_runtime_is_irq_safe(struct device *dev);
> > +    - return true if power.irq_safe flag was set for the device, causing
> > +      the runtime-PM callbacks to be invoked with interrupts off
> > +
> >    void pm_runtime_mark_last_busy(struct device *dev);
> >      - set the power.last_busy field to the current time
> >  
-- 
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