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From: Ulf Hansson <ulf.hansson@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Kevin Hilman <khilman@linaro.org>,
	Tomasz Figa <tomasz.figa@gmail.com>,
	Philipp Zabel <philipp.zabel@gmail.com>,
	Russell King <linux@arm.linux.org.uk>,
	Mark Brown <broonie@kernel.org>, Wolfram Sang <wsa@the-dreams.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Jack Dai <jack.dai@rock-chips.com>,
	Jinkun Hong <jinkun.hong@rock-chips.com>
Subject: Re: [PATCH 0/4] PM / Domains: Fix race conditions during boot
Date: Thu, 2 Oct 2014 12:07:43 +0200	[thread overview]
Message-ID: <CAPDyKFpyGRtrRA4BuvkSHhvZ+DnMFYh-jS2k8VLKo1VMGSSgDw@mail.gmail.com> (raw)
In-Reply-To: <2138676.3O5bPrOhTg@vostro.rjw.lan>

[...]

>> 1) Even if CONFIG_PM_RUNTIME is enabled, we have no mechanism to use
>> for drivers/subsystems to bring device's PM domains into powered state
>> before doing ->probe(). Well, of course, they could use
>> pm_runtime_get_sync() in that path, but that's just not the common
>> practice and there are good reasons to why.
>>
>> So, even if we figured out a solution for drivers/subsystems to
>> support the above, it's not reasonable to think we can adopt each of
>> them shortly. We need a fix in genpd.
>
> My concern is that if we change the default behavior today, people will see
> power regressions on some platforms.  Surely, power regressions are not as
> bad as functional regressions, but we can't say we don't care.
>
> Did you consider adding some handling of that to driver_probe_device()?
> We do a barrier in there, but conceivably we could do more if a PM domain
> is attached.

Forgot to comment on this.

I think the problem with such approach would be that the PM domain
hasn't yet been attached to the device, since that happens at
bus->probe().

Maybe we could find a solution which only affect the buses though and
not the drivers. But I need to think a bit more on this, before I can
post a proposal.

Kind regards
Uffe

      parent reply	other threads:[~2014-10-02 10:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-30 12:43 [PATCH 0/4] PM / Domains: Fix race conditions during boot Ulf Hansson
2014-09-30 12:43 ` [PATCH 1/4] PM / Domains: Remove pm_genpd_dev_need_restore() API Ulf Hansson
2014-09-30 13:21   ` Geert Uytterhoeven
2014-09-30 18:07   ` Kevin Hilman
2014-09-30 12:43 ` [PATCH 2/4] ARM: exynos: Ensure PM domains are powered at initialization Ulf Hansson
2014-09-30 18:33   ` Kevin Hilman
2014-10-01 11:23     ` Tomasz Figa
2014-10-01 12:45       ` Ulf Hansson
2014-09-30 12:43 ` [PATCH 3/4] PM / Domains: Expect PM domains being " Ulf Hansson
2014-09-30 13:24   ` Geert Uytterhoeven
2014-09-30 18:21   ` Kevin Hilman
2014-10-01 11:09     ` Ulf Hansson
2014-09-30 18:30   ` Kevin Hilman
2014-10-01 10:47     ` Ulf Hansson
2014-09-30 12:43 ` [PATCH 4/4] PM / Domains: Enforce PM domains to stay powered during boot Ulf Hansson
2014-09-30 20:08 ` [PATCH 0/4] PM / Domains: Fix race conditions " Rafael J. Wysocki
2014-10-01  7:35   ` Ulf Hansson
2014-10-01 20:31     ` Rafael J. Wysocki
2014-10-02  9:28       ` Ulf Hansson
2014-10-02 10:07       ` Ulf Hansson [this message]

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