linux-kernel - Re: [RFC PATCH 2/5] clockevents: Add generic timer broadcast receiver

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Date:	Wed, 2 Jan 2013 10:59:20 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"nico@...aro.org" <nico@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Will Deacon <Will.Deacon@....com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 2/5] clockevents: Add generic timer broadcast
 receiver

On Fri, Dec 21, 2012 at 10:02:18AM +0000, Santosh Shilimkar wrote:
> On Tuesday 18 December 2012 05:36 PM, Mark Rutland wrote:
> > Currently the broadcast mechanism used for timers is abstracted by a
> > function pointer on struct clock_event_device. As the fundamental
> > mechanism for broadcast is architecture-specific, this ties each
> > clock_event_device driver to a single architecture, even where the
> > driver is otherwise generic.
> >
> > This patch adds a standard path for the receipt of timer broadcasts, so
> > drivers and/or architecture backends need not manage redundant lists of
> > timers for the purpose of routing broadcast timer ticks.
> >
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > ---
> >   include/linux/clockchips.h   |    4 ++++
> >   kernel/time/tick-broadcast.c |   15 +++++++++++++++
> >   2 files changed, 19 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
> > index 8a7096f..e1089aa 100644
> > --- a/include/linux/clockchips.h
> > +++ b/include/linux/clockchips.h
> > @@ -161,6 +161,10 @@ clockevents_calc_mult_shift(struct clock_event_device *ce, u32 freq, u32 minsec)
> >   extern void clockevents_suspend(void);
> >   extern void clockevents_resume(void);
> >
> > +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> > +extern int tick_receive_broadcast(void);
> > +#endif
> > +
> As mentioned in earlier patch, CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> isn't must for SMP kernel and hence when build with
> !GENERIC_CLOCKEVENTS_BROADCAST, $subject patch will break the build.

I'd assumed that the broadcast receive path would be ifdef'd on
CONFIG_GENERIC_CLOCKEVENTS_BROADCAST, and thus this wouldn't be a problem.
Though I guess it probably makes arch/platform code a bit nicer if it doesn't
have to ifdef everything.

> Below is the fix for the same. Feel free to fold it if you agree.

Will do.

> diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
> index 6634652..921568b 100644
> --- a/include/linux/clockchips.h
> +++ b/include/linux/clockchips.h
> @@ -168,6 +168,11 @@ extern void tick_broadcast(const struct cpumask *mask);
>   #define tick_broadcast	NULL
>   #endif
>   extern int tick_receive_broadcast(void);
> +#else
> +static inline int tick_receive_broadcast(void)
> +{
> +	return 0;
> +}
>   #endif
> 
>   #ifdef CONFIG_GENERIC_CLOCKEVENTS
> 

Thanks,
Mark.

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