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@xxxxxxxxx>
---
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 8c53125..2866612 100644
--- a/arch/arm/plat-omap/common.c
+++ b/arch/arm/plat-omap/common.c
@@ -220,20 +220,16 @@ 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)
--
1.5.4.3
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