s390,time: revert direct ktime path for s390 clockevent device
Git commit 4f37a68cda
"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>
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@ -108,20 +108,10 @@ static void fixup_clock_comparator(unsigned long long delta)
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set_clock_comparator(S390_lowcore.clock_comparator);
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}
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static int s390_next_ktime(ktime_t expires,
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static int s390_next_event(unsigned long delta,
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struct clock_event_device *evt)
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{
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struct timespec ts;
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u64 nsecs;
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ts.tv_sec = ts.tv_nsec = 0;
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monotonic_to_bootbased(&ts);
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nsecs = ktime_to_ns(ktime_add(timespec_to_ktime(ts), expires));
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do_div(nsecs, 125);
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S390_lowcore.clock_comparator = sched_clock_base_cc + (nsecs << 9);
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/* Program the maximum value if we have an overflow (== year 2042) */
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if (unlikely(S390_lowcore.clock_comparator < sched_clock_base_cc))
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S390_lowcore.clock_comparator = -1ULL;
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S390_lowcore.clock_comparator = get_tod_clock() + delta;
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set_clock_comparator(S390_lowcore.clock_comparator);
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return 0;
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}
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@ -146,15 +136,14 @@ void init_cpu_timer(void)
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cpu = smp_processor_id();
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cd = &per_cpu(comparators, cpu);
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cd->name = "comparator";
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cd->features = CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_KTIME;
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cd->features = CLOCK_EVT_FEAT_ONESHOT;
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cd->mult = 16777;
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cd->shift = 12;
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cd->min_delta_ns = 1;
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cd->max_delta_ns = LONG_MAX;
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cd->rating = 400;
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cd->cpumask = cpumask_of(cpu);
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cd->set_next_ktime = s390_next_ktime;
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cd->set_next_event = s390_next_event;
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cd->set_mode = s390_set_mode;
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clockevents_register_device(cd);
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