linux-kernel - Re: [PATCH] PM / suspend: Always use deepest C-state in the "freeze" sleep state

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Message-ID: <20140509141356.GA1811@xo-6d-61-c0.localdomain>
Date:	Fri, 9 May 2014 16:13:56 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Aubrey Li <aubrey.li@...el.com>
Subject: Re: [PATCH] PM / suspend: Always use deepest C-state in the "freeze"
 sleep state

On Fri 2014-05-09 13:26:47, Rafael J. Wysocki wrote:
> On Friday, May 09, 2014 09:38:35 AM Pavel Machek wrote:
> > On Mon 2014-05-05 00:51:54, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > If freeze_enter() is called, we want to bypass the current cpuidle
> > > governor and always use the deepest available (that is, not disabled)
> > > C-state, because we want to save as much energy as reasonably possible
> > > then and runtime latency constraints don't matter at that point, since
> > > the system is in a sleep state anyway.
> > 
> > Would there be way to pass the parameter "go to deepest" instead of adding
> > global state for this?
> 
> I'm not sure what you mean?  A parameter of what in particular?  And where
> to pass it?

Currently the code is:

static void freeze_enter(void)
{
+ cpuidle_use_deepest_state(true);
  cpuidle_resume();
  wait_event(suspend_freeze_wait_head, suspend_freeze_wake);
  cpuidle_pause();
+ cpuidle_use_deepest_state(false);
}

. I believe it would be better if you did

cpuidle_resume(GOTO_DEEPEST_C_STATE)

instead of having global state.

Thanks,
										Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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