linux-kernel - Re: [PATCH v2] clocksource: atmel-pit: register as a sched

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Message-ID: <20160224162046.GA28743@finsecur.com>
Date:	Wed, 24 Feb 2016 17:20:46 +0100
From:	Sylvain Rochet <sylvain.rochet@...secur.com>
To:	Romain Izard <romain.izard.pro@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] clocksource: atmel-pit: register as a sched_clock

Hi,

On Wed, Feb 24, 2016 at 05:04:42PM +0100, Romain Izard wrote:
> Register the counter of the Periodic Interval Timer as a possible source
> for sched_clock. Keep the timer running even if the related clockevent
> is disabled.
> 
> This provides a better precision than the jiffies-based default. The
> TCB clocksource does not work, as it is registered too late in the
> initialization sequence.

I have mixed feelings about that, but this is probably just a 
misunderstanding from my part.

The PIT timer should not be used for systems with PM_SUSPEND enabled and 
used because it takes ages to synchronize on resume, how does this patch 
affect that ?

Ref: commit ac34ad27fc ("clockevents: Do not suspend/resume if unused")

Sylvain