Merge branch 'formingo/3.2/tip/timers/core' of git://git.linaro.org/people/jstultz/linux into timers/core
Conflicts: kernel/time/timekeeping.c
This commit is contained in:
commit
367177e501
3 changed files with 57 additions and 11 deletions
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@ -156,6 +156,7 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
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* @mult: cycle to nanosecond multiplier
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* @shift: cycle to nanosecond divisor (power of two)
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* @max_idle_ns: max idle time permitted by the clocksource (nsecs)
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* @maxadj maximum adjustment value to mult (~11%)
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* @flags: flags describing special properties
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* @archdata: arch-specific data
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* @suspend: suspend function for the clocksource, if necessary
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@ -172,7 +173,7 @@ struct clocksource {
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u32 mult;
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u32 shift;
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u64 max_idle_ns;
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u32 maxadj;
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#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
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struct arch_clocksource_data archdata;
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#endif
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@ -491,6 +491,22 @@ void clocksource_touch_watchdog(void)
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clocksource_resume_watchdog();
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}
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/**
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* clocksource_max_adjustment- Returns max adjustment amount
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* @cs: Pointer to clocksource
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*
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*/
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static u32 clocksource_max_adjustment(struct clocksource *cs)
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{
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u64 ret;
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/*
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* We won't try to correct for more then 11% adjustments (110,000 ppm),
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*/
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ret = (u64)cs->mult * 11;
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do_div(ret,100);
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return (u32)ret;
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}
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/**
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* clocksource_max_deferment - Returns max time the clocksource can be deferred
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* @cs: Pointer to clocksource
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@ -503,25 +519,28 @@ static u64 clocksource_max_deferment(struct clocksource *cs)
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/*
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* Calculate the maximum number of cycles that we can pass to the
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* cyc2ns function without overflowing a 64-bit signed result. The
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* maximum number of cycles is equal to ULLONG_MAX/cs->mult which
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* is equivalent to the below.
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* max_cycles < (2^63)/cs->mult
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* max_cycles < 2^(log2((2^63)/cs->mult))
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* max_cycles < 2^(log2(2^63) - log2(cs->mult))
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* max_cycles < 2^(63 - log2(cs->mult))
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* max_cycles < 1 << (63 - log2(cs->mult))
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* maximum number of cycles is equal to ULLONG_MAX/(cs->mult+cs->maxadj)
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* which is equivalent to the below.
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* max_cycles < (2^63)/(cs->mult + cs->maxadj)
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* max_cycles < 2^(log2((2^63)/(cs->mult + cs->maxadj)))
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* max_cycles < 2^(log2(2^63) - log2(cs->mult + cs->maxadj))
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* max_cycles < 2^(63 - log2(cs->mult + cs->maxadj))
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* max_cycles < 1 << (63 - log2(cs->mult + cs->maxadj))
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* Please note that we add 1 to the result of the log2 to account for
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* any rounding errors, ensure the above inequality is satisfied and
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* no overflow will occur.
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*/
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max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1));
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max_cycles = 1ULL << (63 - (ilog2(cs->mult + cs->maxadj) + 1));
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/*
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* The actual maximum number of cycles we can defer the clocksource is
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* determined by the minimum of max_cycles and cs->mask.
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* Note: Here we subtract the maxadj to make sure we don't sleep for
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* too long if there's a large negative adjustment.
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*/
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max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
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max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift);
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max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult - cs->maxadj,
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cs->shift);
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/*
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* To ensure that the clocksource does not wrap whilst we are idle,
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@ -640,7 +659,6 @@ static void clocksource_enqueue(struct clocksource *cs)
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void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
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{
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u64 sec;
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/*
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* Calc the maximum number of seconds which we can run before
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* wrapping around. For clocksources which have a mask > 32bit
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@ -661,6 +679,20 @@ void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
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clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
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NSEC_PER_SEC / scale, sec * scale);
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/*
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* for clocksources that have large mults, to avoid overflow.
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* Since mult may be adjusted by ntp, add an safety extra margin
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*
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*/
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cs->maxadj = clocksource_max_adjustment(cs);
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while ((cs->mult + cs->maxadj < cs->mult)
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|| (cs->mult - cs->maxadj > cs->mult)) {
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cs->mult >>= 1;
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cs->shift--;
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cs->maxadj = clocksource_max_adjustment(cs);
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}
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cs->max_idle_ns = clocksource_max_deferment(cs);
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}
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EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
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@ -701,6 +733,12 @@ EXPORT_SYMBOL_GPL(__clocksource_register_scale);
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*/
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int clocksource_register(struct clocksource *cs)
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{
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/* calculate max adjustment for given mult/shift */
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cs->maxadj = clocksource_max_adjustment(cs);
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WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
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"Clocksource %s might overflow on 11%% adjustment\n",
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cs->name);
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/* calculate max idle time permitted for this clocksource */
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cs->max_idle_ns = clocksource_max_deferment(cs);
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@ -850,6 +850,13 @@ static void timekeeping_adjust(s64 offset)
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} else /* No adjustment needed */
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return;
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WARN_ONCE(timekeeper.clock->maxadj &&
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(timekeeper.mult + adj > timekeeper.clock->mult +
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timekeeper.clock->maxadj),
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"Adjusting %s more then 11%% (%ld vs %ld)\n",
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timekeeper.clock->name, (long)timekeeper.mult + adj,
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(long)timekeeper.clock->mult +
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timekeeper.clock->maxadj);
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/*
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* So the following can be confusing.
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*
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