linux-kernel - Re: [PATCH v7 1/5] PM / Runtime: Add getter for quering the IRQ safe option

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Date:	Wed, 24 Sep 2014 15:47:17 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	<linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Michal Simek <michal.simek@...inx.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	<linux-doc@...r.kernel.org>, <linux-pm@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v7 1/5] PM / Runtime: Add getter for quering the IRQ safe
 option

On Wed, 24 Sep 2014, Pavel Machek wrote:

> On Wed 2014-09-24 15:50:08, Krzysztof Kozlowski wrote:
> > Add a simple getter pm_runtime_is_irq_safe() for quering 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@...sung.com>
> > Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
> 
> Are you sure this is good interface?
> 
> "Tell me if another function works this or that way".
> 
> That's certainly not traditional interface, and it seems dangerous to
> me. Callbacks now have different semantic requirements based on value
> of some flag...
> 
> Would it be possible to have two sets of callbacks, one irq safe and
> one not?

Or maybe add a flag to the bus-specific device structures, indicating
specifically whether or not the clock should be unprepared during a
runtime suspend.  Then individual drivers could set this flag or not, 
independent of the irq-safe setting.

Alan Stern

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