From 80ea3bac3a47bc73efa334d0dd57099d0ff14216 Mon Sep 17 00:00:00 2001 From: Aaro Koskinen Date: Wed, 4 Mar 2009 10:07:41 -0800 Subject: [PATCH] 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 Signed-off-by: Tony Lindgren --- arch/arm/plat-omap/common.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c index 0843b8882f9..6825fbb5a05 100644 --- a/arch/arm/plat-omap/common.c +++ b/arch/arm/plat-omap/common.c @@ -199,21 +199,17 @@ static struct clocksource clocksource_32k = { .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 * 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) -- 2.20.1