From 6e35994d1f6831af1e5577e28c363c9137d7d597 Mon Sep 17 00:00:00 2001 From: Bharat Bhushan Date: Wed, 18 Apr 2012 06:01:19 +0000 Subject: KVM: PPC: Use clockevent multiplier and shifter for decrementer Time for which the hrtimer is started for decrementer emulation is calculated using tb_ticks_per_usec. While hrtimer uses the clockevent for DEC reprogramming (if needed) and which calculate timebase ticks using the multiplier and shifter mechanism implemented within clockevent layer. It was observed that this conversion (timebase->time->timebase) are not correct because the mechanism are not consistent. In our setup it adds 2% jitter. With this patch clockevent multiplier and shifter mechanism are used when starting hrtimer for decrementer emulation. Now the jitter is < 0.5%. Signed-off-by: Bharat Bhushan Signed-off-by: Alexander Graf --- arch/powerpc/kernel/time.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/time.c') diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2c42cd72d0f5..99a995c2a3f2 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -100,7 +100,7 @@ static int decrementer_set_next_event(unsigned long evt, static void decrementer_set_mode(enum clock_event_mode mode, struct clock_event_device *dev); -static struct clock_event_device decrementer_clockevent = { +struct clock_event_device decrementer_clockevent = { .name = "decrementer", .rating = 200, .irq = 0, @@ -108,6 +108,7 @@ static struct clock_event_device decrementer_clockevent = { .set_mode = decrementer_set_mode, .features = CLOCK_EVT_FEAT_ONESHOT, }; +EXPORT_SYMBOL(decrementer_clockevent); DEFINE_PER_CPU(u64, decrementers_next_tb); static DEFINE_PER_CPU(struct clock_event_device, decrementers); -- cgit v1.2.1