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authorStephen Boyd <sboyd@codeaurora.org>2013-07-18 16:21:14 -0700
committerJohn Stultz <john.stultz@linaro.org>2013-07-30 11:24:20 -0700
commit87d8b9eb7eb6669aad6435a51e9862362141ba76 (patch)
tree904750465607175129393328e299fb9474adb604 /kernel/time/clocksource.c
parentad81f0545ef01ea651886dddac4bef6cec930092 (diff)
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.c45
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