Date: Mon, 10 Nov 2014 11:36:10 -0500 (EST)
From: Alan Stern <stern@rowland.harvard.edu>
To: Ulf Hansson <ulf.hansson@linaro.org>
cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Russell King <linux@arm.linux.org.uk>,
        Dan Williams <dan.j.williams@intel.com>,
        Vinod Koul <vinod.koul@intel.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        <dmaengine@vger.kernel.org>, Lars-Peter Clausen <lars@metafoo.de>,
        Michal Simek <michal.simek@xilinx.com>,
        Kevin Hilman <khilman@kernel.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no
 PM_RUNTIME
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Message-ID: <Pine.LNX.4.44L0.1411101133100.5793-100000@netrider.rowland.org>
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On Mon, 10 Nov 2014, Ulf Hansson wrote:

> > To me, this sounds like a good reason to avoid using
> > force_runtime_suspend().  In fact, it sounds like a good reason to
> > avoid relying on the runtime PM mechanism to handle non-runtime-PM
> > things (like a system suspend callback).  If CONFIG_PM_RUNTIME isn't
> > enabled then the runtime PM stack simply should not be used.
> 
> There are an important advantage of using the pm_runtime_force_suspend() here.
> 
> For the driver to handle clock gating at system PM suspend, it first
> needs to bring the device into full power, through
> pm_runtime_get_sync(). Otherwise it's not safe to gate the clock,
> since it may already be gated.

That's fine, but it has nothing to do with pm_runtime_force_suspend().

Besides, if the real question is whether or not to gate the clock (or 
in other words, has the clock already been gated), why not just store a 
"clock_is_gated" flag somewhere?

Alan Stern

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