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Message-ID: <20130620150321.GH10269@tarshish>
Date: Thu, 20 Jun 2013 18:03:21 +0300
From: Baruch Siach <baruch@...s.co.il>
To: Pavel Machek <pavel@...x.de>
Cc: John Stultz <john.stultz@...aro.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Jamie Iles <jamie@...ieiles.com>,
Dinh Nguyen <dinguyen@...era.com>
Subject: Re: [RFC PATCH 2/2] clocksource: dw_apb: allow build for
architectures other than arm
Hi Pavel,
On Thu, Jun 20, 2013 at 04:44:33PM +0200, Pavel Machek wrote:
> > > >@@ -73,6 +77,9 @@ static void add_clocksource(struct device_node
> > > > *source_timer)
> > > > }
> > > > static void __iomem *sched_io_base;
> > > >+#ifndef CONFIG_HAVE_SETUP_SCHED_CLOCK
> > > >+static u64 sched_clock_mult __read_mostly;
> > > >+#endif
> > > > static u32 read_sched_clock(void)
> > > > {
> > > >@@ -97,7 +104,11 @@ static void init_sched_clock(void)
> > > > timer_get_base_and_rate(sched_timer, &sched_io_base, &rate);
> > > > of_node_put(sched_timer);
> > > >+#ifdef CONFIG_HAVE_SETUP_SCHED_CLOCK
> > > > setup_sched_clock(read_sched_clock, 32, rate);
> > > >+#else
> > > >+ sched_clock_mult = NSEC_PER_SEC / rate;
> > > >+#endif
> > > > }
> > >
> > > Can you rework this to not use #ifdefs within the function? They
> > > make it annoying to read the code.
> > >
> > > Instead maybe have a local setup_sched_clock() function that sets
> > > the mult value for the !CONFIG_HAVE_SETUP_SCHED_CLOCK case?
> > >
> > > > static const struct of_device_id osctimer_ids[] __initconst = {
> > > >@@ -124,3 +135,10 @@ void __init dw_apb_timer_init(void)
> > > > init_sched_clock();
> > > > }
> > > >+
> > > >+#ifndef CONFIG_HAVE_SETUP_SCHED_CLOCK
> > > >+unsigned long long notrace sched_clock()
> > > >+{
> > > >+ return read_sched_clock() * sched_clock_mult;
> > > >+}
> > > >+#endif
> > >
> > > Also, can you try to condense the number of #ifndef
> > > CONFIG_HAVE_SETUP_SCHED_CLOCK checks to one, and consolidate the
> > > needed functions all in that one conditional?
> >
> > Thanks for your comments. I'll rework the patch and resubmit.
> >
> > I've just noticed that I have a bigger problem. read_sched_clock() returns
> > u32, not u64. This means that in a rate of, say, 100MHz it will wrap around
> > after a little more than 40 seconds. Would it make sense to put ARM's 32 bin
> > sched_clock extension code (arch/arm/kernel/sched_clock.c) is a common place
> > (maybe drivers/clocksource), and use that? There seems to be nothing ARM
> > specific in this code, after all.
>
> Also note that there are two conflicting changes to this area
> pending. It seems one in soc-next arm tree will prevail.
>
> Please take a look...
Now that generic sched_clock implementation is available to all architectures
(38ff87f77 "sched_clock: Make ARM's sched_clock generic for all architectures"
in the timers/core branch of the tip tree) this patch is not needed anymore.
Thanks for the head up.
baruch
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