linux-kernel - Re: [PATCH v1] clocksource: atmel-pit: register as a sched

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Message-ID: <20160208150614.5e87133e@bbrezillon>
Date:	Mon, 8 Feb 2016 15:06:14 +0100
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Romain Izard <romain.izard.pro@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: Re: [PATCH v1] clocksource: atmel-pit: register as a sched_clock

+ Alexandre

Hi Daniel,

On Mon, 8 Feb 2016 14:33:04 +0100
Daniel Lezcano <daniel.lezcano@...aro.org> wrote:

> On 02/04/2016 06:21 PM, Romain Izard wrote:
> > Register the counter of the Periodic Interval Timer as a possible source
> > for sched_clock. This provides a better precision than the jiffies-based
> > default.
> >
> > Signed-off-by: Romain Izard <romain.izard.pro@...il.com>
> 
> Nicolas, Boris,
> 
> Are you ok with this patch ?

Not sure yet :). On most platforms we are also declaring a clocksource
based on the TCB IP, and this one provides a better precision than the
PIT clocksource.
What happens if the PIT is de-activated while it's still supposed to
provide the sched_clock(). Is there a way to flag the clocksource as
still needed so that the core does not shut it down by when the TCB
clocksource comes in.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com