linux-kernel - Re: [RFC 2/2] clocksource: don't suspend/resume when unused

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Message-ID: <20150116114521.GQ3843@piout.net>
Date:	Fri, 16 Jan 2015 12:45:21 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/2] clocksource: don't suspend/resume when unused

On 16/01/2015 at 12:07:42 +0100, Alexandre Belloni wrote :
> On 16/01/2015 at 11:59:33 +0100, Daniel Lezcano wrote :
> > On 01/16/2015 11:48 AM, Alexandre Belloni wrote:
> > >Hi,
> > >
> > >On 16/01/2015 at 11:39:16 +0100, Daniel Lezcano wrote :
> > >>>Isn't that already the case?
> > >>>Right now, if you call clocksource_suspend, it doesn't matter whether
> > >>>the clocksource has an enable or not, it will be suspended. Maybe I'm
> > >>>mistaken but my patch doesn't seem to change that behaviour.
> > >>
> > >>Actually, if there is no enable/disable callback, then CLOCK_SOURCE_USED
> > >>will be never set, hence the condition will always fail and the suspend
> > >>callback won't be called.
> > >>
> > >
> > >It is set in clocksource_enable/disable, even if there is no
> > >enable/disable callback.
> > 
> > Ah, right. But shouldn't we set the flag only if the callback is present and
> > succeed as Boris mentioned it ?
> > 
> 
> What Boris was suggesting was that if the enable exist, set it only if
> it succeed. Which gives something like that:
> 
> int clocksource_enable(struct clocksource *cs)
> {
> 	int ret = 0;
> 
> 	if (cs->enable)
> 		ret = cs->enable(cs);
> 
> 	if (!ret)
> 		cs->flags |= CLOCK_SOURCE_USED;
> 
> 	return 0;

Obviously, that is

return ret;



> }
> 
> I will use that version in v2.
> 
> 
> -- 
> Alexandre Belloni, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com

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