linux-kernel - Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no PM

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Message-ID: <CAPDyKFp+cZa6PrAwQHbQE4xEzmRKBwN5J_uRByOdM0h8yoV2vg@mail.gmail.com>
Date:	Mon, 10 Nov 2014 19:35:39 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Russell King <linux@....linux.org.uk>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
	Michal Simek <michal.simek@...inx.com>,
	Kevin Hilman <khilman@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no PM_RUNTIME

On 10 November 2014 17:36, Alan Stern <stern@...land.harvard.edu> wrote:
> 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?

You could do that, but it's easier to not.

You will need to update the runtime PM status and disable runtime PM
anyway, done by the API.

Kind regards
Uffe
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