linux-kernel - Re: [PATCH] cpufreq: suspend/resume governors with PM notifiers

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Date:	Sat, 16 Nov 2013 20:47:24 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	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] cpufreq: suspend/resume governors with PM notifiers

On 16 November 2013 19:59, Rafael J. Wysocki <rjw@...ysocki.net> wrote:

> Well, disabling it for the whole duration of suspend/resume and/or hibernation
> may not be the right approach entirely, unless we force the pax perf of the

s/pax/max ?

> boot CPU at least in addition to that.  Otherwise the latency of suspend and
> the subsequent resume will depend on what perf level the CPUs where before
> disabling the governors, which is not desirable at al.

Well that is pretty much doable.

>> And these are the notifications that we send:
>> - PM_HIBERNATION_PREPARE
>> - PM_POST_HIBERNATION
>> - PM_RESTORE_PREPARE
>> - PM_POST_RESTORE
>>
>> If I am not wrong I need to stop governors on PM_HIBERNATION_PREPARE and need to
>> start them back on: PM_POST_HIBERNATION (I am a bit confused with this one. Does
>> this POST_HIBERNATION one happens at the end of going into hibernation? or after
>> booting back? I need a notifier at the end of restore)..
>
> You'd need both PM_POST_HIBERNATION and PM_POST_RESTORE, but I wouldn't really
> like cpufreq governors to be disabled throughout the whole hibernation.

So PM_POST_HIBERNATION is called just before shutting off the system? And
PM_POST_RESTORE is called after system is resumed from saved image?

> Actually, we use CPU offline/online during system suspend/resume to avoid
> having to do stuff like this from PM notifiers.

I didn't get the logic behind this one..

> So I'd like the original problem to be addressed in a different way.

Hmm..

> PS
> The sisk.pl address will start bouncing shortly, so please replace it with
> rjw@...ysocki.net in your address book.

Okay...
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