linux-kernel - Re: [PATCH v3] ARM: tegra: cpuidle: implement cpuidle_state.enter

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Date:	Mon, 29 Jun 2015 11:18:49 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Russell King <linux@....linux.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Ingo Molnar <mingo@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ARM: tegra: cpuidle: implement cpuidle_state.enter_freeze()

On 29 June 2015 at 11:00, Thierry Reding <thierry.reding@...il.com> wrote:
> On Thu, Jun 18, 2015 at 09:09:29AM +0200, Tomeu Vizoso wrote:
>> On 21 May 2015 at 03:02, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> > On Tuesday, May 19, 2015 04:49:12 PM Tomeu Vizoso wrote:
>> >> This callback is expected to do the same as enter() but it has to
>> >> guarantee that interrupts aren't enabled at any point in its execution,
>> >> as the tick is frozen.
>> >>
>> >> It will be called when the system goes to suspend-to-idle and will
>> >> reduce power usage because CPUs won't be awaken for unnecessary IRQs.
>> >>
>> >> By setting the CPUIDLE_FLAG_TIMER_STOP flag, we can reuse the same code
>> >> for both the enter() and enter_freeze() callbacks.
>> >>
>> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
>> >> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> >
>> > Makes sense to me, but I suppose it should go in via arm-soc.
>>
>> Hi Thierry,
>>
>> what's the plan regarding merging of this patch?
>>
>> It needs df8d9ee ("cpuidle: Run tick_broadcast_exit() with disabled
>> interrupts") so it doesn't break boot.
>
> By the looks of it the above patch was merged in 4.1, so I can easily
> take this through the Tegra tree. The commit message doesn't say whether
> or not this fixes a bug. Is this urgent? Should it go into 4.2? It
> sounds more like it's a power-saving feature, so 4.3 is probably more
> appropriate.

Yeah, it doesn't fix any bug and its effect should only be reduced
power consumption when in suspend-to-idle.

Thanks,

Tomeu

> Thierry
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