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ARM: OMAP: sched_clock() corrected

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After my OMAP3 board has been running for a while, I'm seeing weird
latency traces like this:

      sh-1574    0d.h2  153us : do_timer (tick_do_update_jiffies64)
      sh-1574    0d.h2  153us : update_wall_time (do_timer)
      sh-1574    0d.h2  153us!: omap_32k_read (update_wall_time)
      sh-1574    0d.h2 1883us : update_xtime_cache (update_wall_time)
      sh-1574    0d.h2 1883us : clocksource_get_next (update_wall_time)
      sh-1574    0d.h2 1883us+: _spin_lock_irqsave (clocksource_get_next)

and after a while:

      sh-17818   0d.h3  153us : do_timer (tick_do_update_jiffies64)
      sh-17818   0d.h3  153us : update_wall_time (do_timer)
      sh-17818   0d.h3  153us!: omap_32k_read (update_wall_time)
      sh-17818   0d.h3 1915us : update_xtime_cache (update_wall_time)
      sh-17818   0d.h3 1915us+: clocksource_get_next (update_wall_time)
      sh-17818   0d.h3 1945us : _spin_lock_irqsave (clocksource_get_next)

Turns out that sched_clock() is using cyc2ns(), which returns NTP
adjusted time. The sched_clock() frequency should not be adjusted. The
patch deletes omap_32k_ticks_to_nsecs() and rewrites sched_clock()
to do the conversion using the constant multiplier.

Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This commit is contained in:
Aaro Koskinen 2009-03-04 10:07:41 -08:00 • committed by Tony Lindgren
parent 87d99d6f7e
commit 80ea3bac3a
1 changed files with 5 additions and 9 deletions
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14
arch/arm/plat-omap/common.c
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@ -199,21 +199,17 @@ static struct clocksource clocksource_32k = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS, .flags = CLOCK_SOURCE_IS_CONTINUOUS,
}; };
/*
* Rounds down to nearest nsec.
*/
unsigned long long omap_32k_ticks_to_nsecs(unsigned long ticks_32k)
{
return cyc2ns(&clocksource_32k, ticks_32k);
}
/* /*
* Returns current time from boot in nsecs. It's OK for this to wrap * Returns current time from boot in nsecs. It's OK for this to wrap
* around for now, as it's just a relative time stamp. * around for now, as it's just a relative time stamp.
*/ */
unsigned long long sched_clock(void) unsigned long long sched_clock(void)
{ {
return omap_32k_ticks_to_nsecs(omap_32k_read()); unsigned long long ret;
ret = (unsigned long long)omap_32k_read();
ret = (ret * clocksource_32k.mult_orig) >> clocksource_32k.shift;
return ret;
} }
static int __init omap_init_clocksource_32k(void) static int __init omap_init_clocksource_32k(void)