linux-kernel - Re: [PATCH] clocksource: timer-atmel-pit: don't suspend/resume if unused

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Date:	Thu, 15 Jan 2015 12:52:09 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	sylvain.rochet@...secur.com
Subject: Re: [PATCH] clocksource: timer-atmel-pit: don't suspend/resume if
 unused

Hi,

I'll do it but only if you review my other series :)

On 15/01/2015 at 12:41:27 +0100, Daniel Lezcano wrote :
> On 01/13/2015 11:47 AM, Thomas Gleixner wrote:
> >On Mon, 12 Jan 2015, Daniel Lezcano wrote:
> >
> >>On 01/12/2015 03:04 PM, Nicolas Ferre wrote:
> >>>Le 18/12/2014 15:05, Nicolas Ferre a écrit :
> >>>>From: Sylvain Rochet <sylvain.rochet@...secur.com>
> >>>>
> >>>>Waiting for PIT to stop counting takes a long time:
> >>>>    1/(Master clock/prescaler/PIVR)
> >>>>= 1/(133 MHz     /16       /2^20)
> >>>>= 126 ms
> >>>>
> >>>>Up to 126 ms if master clock is set to 133 MHz, skipping suspend/resume
> >>>>of the unused PIT device reduce (suspend time + resume time) from ~140 ms
> >>>>to ~17 ms.
> >>>>
> >>>>Signed-off-by: Sylvain Rochet <sylvain.rochet@...secur.com>
> >>>>[nicolas.ferre@...el.com: move to newer clocksource driver]
> >>>>Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> >>>>Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> >>>>---
> >>>>Hi Sylvain,
> >>>>
> >>>>I re-worked (and "Acked") your patch so it can be applied on the newer
> >>>>Mainline
> >>>>kernels. Beware, I changed the "subject line" as well. The PIT driver
> >>>>moved
> >>>>recently (3.18).
> >>>>
> >>>>Daniel,
> >>>>Can you take this patch in your tree?
> >>>
> >>>Hi Daniel,
> >>>
> >>>Anything prevents this patch from being merged (aka ping ;-))?
> >>
> >>[Cc'ed tglx].
> >>
> >>Hi Nico,
> >>
> >>thanks for the head up.
> >>
> >>Nothing prevents it but I am wondering if this change shouldn't be in the
> >>generic framework (kernel/time/clocksource.c and kernel/time/clockevents.c),
> >>so all drivers will benefit this change ?
> >
> >Indeed. There is no point in calling suspend/resume for unused
> >clockevents. They should be stopped and disabled already.
> 
> Hi Nico,
> 
> are you planning to do the change in the generic framework ?
> 
> Thanks
>   -- Daniel
> 
> >Now with clocksources this might be different. We have no explicit
> >state for this, but its trivial to add one at least for those
> >clocksources which have enable/disable callbacks. For the other ones
> >not so much.
> 
> 
> 
> 
> 
> -- 
>  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
> 
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> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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