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author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2013-11-22 15:04:18 +0400 |
---|---|---|
committer | Ben Hutchings <ben@decadent.org.uk> | 2015-01-01 04:27:51 +0300 |
commit | 17d1b500792b382169883c1e2415f1e930236128 (patch) | |
tree | 0c3a2e68ffbeb4458a4a5aeec15ccaafb99ab706 /arch/s390 | |
parent | 6d9f360c00512f6a6fded2efcfcbe78ec73e5b1b (diff) | |
download | linux-17d1b500792b382169883c1e2415f1e930236128.tar.xz |
s390,time: revert direct ktime path for s390 clockevent device
commit 8adbf78ec4839c1dc4ff20c9a1f332a7bc99e6e6 upstream.
Git commit 4f37a68cdaf6dea833cfdded2a3e0c47c0f006da
"s390: Use direct ktime path for s390 clockevent device" makes use
of the CLOCK_EVT_FEAT_KTIME clockevent option to avoid the delta
calculation with ktime_get() in clockevents_program_event and the
get_tod_clock() in s390_next_event. This is based on the assumption
that the difference between the internal ktime and the hardware
clock is reflected in the wall_to_monotonic delta. But this is not
true, the ntp corrections are applied via changes to the tk->mult
multiplier and this is not reflected in wall_to_monotonic.
In theory this could be solved by using the raw monotonic clock
but it is simpler to switch back to the standard clock delta
calculation.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[bwh: Backported to 3.2: s/get_tod_clock()/get_clock()/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/s390')
-rw-r--r-- | arch/s390/kernel/time.c | 19 |
1 files changed, 4 insertions, 15 deletions
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index b2f44de079b9..fd65e5e2c7b0 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -110,20 +110,10 @@ static void fixup_clock_comparator(unsigned long long delta) set_clock_comparator(S390_lowcore.clock_comparator); } -static int s390_next_ktime(ktime_t expires, +static int s390_next_event(unsigned long delta, struct clock_event_device *evt) { - struct timespec ts; - u64 nsecs; - - ts.tv_sec = ts.tv_nsec = 0; - monotonic_to_bootbased(&ts); - nsecs = ktime_to_ns(ktime_add(timespec_to_ktime(ts), expires)); - do_div(nsecs, 125); - S390_lowcore.clock_comparator = sched_clock_base_cc + (nsecs << 9); - /* Program the maximum value if we have an overflow (== year 2042) */ - if (unlikely(S390_lowcore.clock_comparator < sched_clock_base_cc)) - S390_lowcore.clock_comparator = -1ULL; + S390_lowcore.clock_comparator = get_clock() + delta; set_clock_comparator(S390_lowcore.clock_comparator); return 0; } @@ -148,15 +138,14 @@ void init_cpu_timer(void) cpu = smp_processor_id(); cd = &per_cpu(comparators, cpu); cd->name = "comparator"; - cd->features = CLOCK_EVT_FEAT_ONESHOT | - CLOCK_EVT_FEAT_KTIME; + cd->features = CLOCK_EVT_FEAT_ONESHOT; 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_ktime = s390_next_ktime; + cd->set_next_event = s390_next_event; cd->set_mode = s390_set_mode; clockevents_register_device(cd); |