diff options
author | Stephen Boyd <sboyd@codeaurora.org> | 2013-07-18 16:21:14 -0700 |
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committer | John Stultz <john.stultz@linaro.org> | 2013-07-30 11:24:20 -0700 |
commit | 87d8b9eb7eb6669aad6435a51e9862362141ba76 (patch) | |
tree | 904750465607175129393328e299fb9474adb604 /kernel/time/clocksource.c | |
parent | ad81f0545ef01ea651886dddac4bef6cec930092 (diff) | |
download | linux-87d8b9eb7eb6669aad6435a51e9862362141ba76.tar.bz2 |
clocksource: Extract max nsec calculation into separate function
We need to calculate the same number in the clocksource code and
the sched_clock code, so extract this code into its own function.
We also drop the min_t and just use min() because the two types
are the same.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'kernel/time/clocksource.c')
-rw-r--r-- | kernel/time/clocksource.c | 45 |
1 files changed, 30 insertions, 15 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 50a8736757f3..637a14af6c21 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -537,40 +537,55 @@ static u32 clocksource_max_adjustment(struct clocksource *cs) } /** - * clocksource_max_deferment - Returns max time the clocksource can be deferred - * @cs: Pointer to clocksource - * + * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted + * @mult: cycle to nanosecond multiplier + * @shift: cycle to nanosecond divisor (power of two) + * @maxadj: maximum adjustment value to mult (~11%) + * @mask: bitmask for two's complement subtraction of non 64 bit counters */ -static u64 clocksource_max_deferment(struct clocksource *cs) +u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask) { u64 max_nsecs, max_cycles; /* * Calculate the maximum number of cycles that we can pass to the * cyc2ns function without overflowing a 64-bit signed result. The - * maximum number of cycles is equal to ULLONG_MAX/(cs->mult+cs->maxadj) + * maximum number of cycles is equal to ULLONG_MAX/(mult+maxadj) * which is equivalent to the below. - * max_cycles < (2^63)/(cs->mult + cs->maxadj) - * max_cycles < 2^(log2((2^63)/(cs->mult + cs->maxadj))) - * max_cycles < 2^(log2(2^63) - log2(cs->mult + cs->maxadj)) - * max_cycles < 2^(63 - log2(cs->mult + cs->maxadj)) - * max_cycles < 1 << (63 - log2(cs->mult + cs->maxadj)) + * max_cycles < (2^63)/(mult + maxadj) + * max_cycles < 2^(log2((2^63)/(mult + maxadj))) + * max_cycles < 2^(log2(2^63) - log2(mult + maxadj)) + * max_cycles < 2^(63 - log2(mult + maxadj)) + * max_cycles < 1 << (63 - log2(mult + maxadj)) * Please note that we add 1 to the result of the log2 to account for * any rounding errors, ensure the above inequality is satisfied and * no overflow will occur. */ - max_cycles = 1ULL << (63 - (ilog2(cs->mult + cs->maxadj) + 1)); + max_cycles = 1ULL << (63 - (ilog2(mult + maxadj) + 1)); /* * The actual maximum number of cycles we can defer the clocksource is - * determined by the minimum of max_cycles and cs->mask. + * determined by the minimum of max_cycles and mask. * Note: Here we subtract the maxadj to make sure we don't sleep for * too long if there's a large negative adjustment. */ - max_cycles = min_t(u64, max_cycles, (u64) cs->mask); - max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult - cs->maxadj, - cs->shift); + max_cycles = min(max_cycles, mask); + max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift); + + return max_nsecs; +} + +/** + * clocksource_max_deferment - Returns max time the clocksource can be deferred + * @cs: Pointer to clocksource + * + */ +static u64 clocksource_max_deferment(struct clocksource *cs) +{ + u64 max_nsecs; + max_nsecs = clocks_calc_max_nsecs(cs->mult, cs->shift, cs->maxadj, + cs->mask); /* * To ensure that the clocksource does not wrap whilst we are idle, * limit the time the clocksource can be deferred by 12.5%. Please |