linux-kernel - Re: [PATCH V2 2/2] cpufreq: Change freq before suspending governors

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Message-ID: <4592811.7DNNYfo4cW@vostro.rjw.lan>
Date:	Fri, 22 Nov 2013 14:25:59 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Stephen Warren <swarren@...dia.com>, Kukjin Kim <kgene@...nel.org>,
	Amit Daniel Kachhap <amit.daniel@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lan Tianyu <tianyu.lan@...el.com>, Nishanth Menon <nm@...com>,
	jinchoi@...adcom.com,
	Sebastian Capella <sebastian.capella@...aro.org>
Subject: Re: [PATCH V2 2/2] cpufreq: Change freq before suspending governors

On Friday, November 22, 2013 06:22:52 PM Viresh Kumar wrote:
> On 22 November 2013 18:07, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > On Friday, November 22, 2013 04:59:49 PM Viresh Kumar wrote:
> >> Some platforms might want to change frequency before suspending governors. Like:
> >> - Some platform which want to set freq to max to speed up suspend/hibernation
> >>   process.
> >> - Some platform (like: Tegra or exynos), set this to min or bootloader's
> >>   frequency.
> >>
> >> This patch adds an option for those, so that they can specify this at call to
> >> ->init(), so that cpufreq core can take care of this before suspending system.
> >>
> >> If this variable is not updated by ->init() then its value would be zero and so
> >> core wouldn't do anything.
> >>
> >> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> >
> > I don't think this is generally necessary, because the suspend/resume routines
> > added by patch [1/2] will be executed very late during suspend or very early
> > during resume and it shouldn't really matter what performance levels the CPUs
> > are at then.
> 
> There are few things here:
> - I feel that the current place from where we have suspended stuff is not gonna
> fly. We are doing that in noirq and probably devices which might be required
> during frequency transitions might already be down.. So we *may* need to
> move that in dpm_suspend()..

That would be a much more intrusive change.  Definitely not 3.13 material
at this point.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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