From 4f37a68cdaf6dea833cfdded2a3e0c47c0f006da Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Tue, 23 Aug 2011 15:29:44 +0200 Subject: [PATCH] s390: Use direct ktime path for s390 clockevent device The clock comparator on s390 uses the same format as the TOD clock. If the value in the clock comparator is smaller than the current TOD value an interrupt is pending. Use the CLOCK_EVT_FEAT_KTIME feature to get the unmodified ktime of the next clockevent expiration and use it to program the clock comparator without querying the TOD clock. Signed-off-by: Martin Schwidefsky Cc: john stultz Link: http://lkml.kernel.org/r/20110823133143.153017933@de.ibm.com Signed-off-by: Thomas Gleixner --- arch/s390/kernel/time.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index dff933065ab6..c53716487e77 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -109,10 +109,14 @@ static void fixup_clock_comparator(unsigned long long delta) set_clock_comparator(S390_lowcore.clock_comparator); } -static int s390_next_event(unsigned long delta, +static int s390_next_ktime(ktime_t expires, struct clock_event_device *evt) { - S390_lowcore.clock_comparator = get_clock() + delta; + s64 nsecs; + + nsecs = ktime_to_ns(ktime_sub(expires, ktime_get_monotonic_offset())); + do_div(nsecs, 125); + S390_lowcore.clock_comparator = TOD_UNIX_EPOCH + (nsecs << 9); set_clock_comparator(S390_lowcore.clock_comparator); return 0; } @@ -137,14 +141,15 @@ void init_cpu_timer(void) cpu = smp_processor_id(); cd = &per_cpu(comparators, cpu); cd->name = "comparator"; - cd->features = CLOCK_EVT_FEAT_ONESHOT; + cd->features = CLOCK_EVT_FEAT_ONESHOT | + CLOCK_EVT_FEAT_KTIME; cd->mult = 16777; cd->shift = 12; cd->min_delta_ns = 1; cd->max_delta_ns = LONG_MAX; cd->rating = 400; cd->cpumask = cpumask_of(cpu); - cd->set_next_event = s390_next_event; + cd->set_next_ktime = s390_next_ktime; cd->set_mode = s390_set_mode; clockevents_register_device(cd);