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

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Message-ID: <20140509073835.GB4965@xo-6d-61-c0.localdomain>
Date:	Fri, 9 May 2014 09:38:35 +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 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?
								Pavel

> Index: linux-pm/kernel/power/suspend.c
> ===================================================================
> --- linux-pm.orig/kernel/power/suspend.c
> +++ linux-pm/kernel/power/suspend.c
> @@ -54,9 +54,11 @@ static void freeze_begin(void)
>  
>  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);
>  }
>  
>  void freeze_wake(void)
> 
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