linux-kernel - Re: [PATCH 39/41] clocksource: vf_pit: Migrate to new 'set-state' interface

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Message-ID: <20150703111747.GG23297@linux>
Date:	Fri, 3 Jul 2015 16:47:47 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Stefan Agner <stefan@...er.ch>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Jingchang Lu <b35083@...escale.com>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [PATCH 39/41] clocksource: vf_pit: Migrate to new 'set-state'
 interface

On 03-07-15, 13:11, Stefan Agner wrote:
> On 2015-07-03 10:57, Viresh Kumar wrote:
> > On 03-07-15, 10:10, Stefan Agner wrote:
> >> >  	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
> >> > -	.set_mode	= pit_set_mode,
> >> > +	.set_state_shutdown = pit_shutdown,
> >> > +	.set_state_periodic = pit_set_periodic,
> >>
> >> I'm not really familiar with the interface, but given that we announce
> >> the feature CLOCK_EVT_FEAT_ONESHOT shouldn't we add a set_state_oneshot
> >> callback here?
> > 
> > We weren't doing anything in pit_set_mode(ONESHOT) and so that
> > callback is not implemented. In case you need to do something in
> > set_state_oneshot(), we can add it back.
> 
> True, weren't doing anything. I wonder if that is right. Afaik, we
> should set the same timer for oneshot too, hence call
> pit_set_next_event. With your change we can just reuse the same function
> (pit_set_periodic) for set_state_oneshot.

pit_set_next_event() will be called by clockevents core directly after
tying to set the device in oneshot mode. And so no changes are
required.

> To maintain the atomicity of the changes, this would need to be fixed in
> a separate patch anyway. So this change looks good to me:
> 
> Acked-by: Stefan Agner <stefan@...er.ch>

Thanks.

> I guess "clockevents: Allow set-state callbacks to be optional" makes it
> before this patch? Otherwise we would call a null pointer...

Yeah, I have mentioned this in the cover-letter that there are
dependencies over clockevent core's next branch.

-- 
viresh
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