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

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Date:	Mon, 29 Jun 2015 11:00:51 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.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 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.

Thierry

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