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| author | Aaro Koskinen <Aaro.Koskinen@nokia.com> | 2009-03-04 18:07:41 (GMT) |
|---|---|---|
| committer | Tony Lindgren <tony@atomide.com> | 2009-03-04 18:07:41 (GMT) |
| commit | 80ea3bac3a47bc73efa334d0dd57099d0ff14216 (patch) | |
| tree | 2312b3917a7ac97bfe59d0419122714a118cbcc3 /arch | |
| parent | 87d99d6f7ee3ec73b2b0212427b173502ec9d6cb (diff) | |
| download | linux-80ea3bac3a47bc73efa334d0dd57099d0ff14216.tar.xz | |
ARM: OMAP: sched_clock() corrected
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/plat-omap/common.c | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c index 0843b88..6825fbb 100644 --- a/arch/arm/plat-omap/common.c +++ b/arch/arm/plat-omap/common.c @@ -200,20 +200,16 @@ static struct clocksource clocksource_32k = { }; /* - * 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 * around for now, as it's just a relative time stamp. */ 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) |