Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[cascardo/linux.git] / arch / x86 / kernel / tsc.c

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index ea03031..b6025f9 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -234,9 +234,6 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
        return ns;
 }
 
-/* XXX surely we already have this someplace in the kernel?! */
-#define DIV_ROUND(n, d) (((n) + ((d) / 2)) / (d))
-
 static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 {
        unsigned long long tsc_now, ns_now;
@@ -259,7 +256,9 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
         * time function is continuous; see the comment near struct
         * cyc2ns_data.
         */
-       data->cyc2ns_mul = DIV_ROUND(NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR, cpu_khz);
+       data->cyc2ns_mul =
+               DIV_ROUND_CLOSEST(NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR,
+                                 cpu_khz);
        data->cyc2ns_shift = CYC2NS_SCALE_FACTOR;
        data->cyc2ns_offset = ns_now -
                mul_u64_u32_shr(tsc_now, data->cyc2ns_mul, CYC2NS_SCALE_FACTOR);
@@ -951,7 +950,7 @@ core_initcall(cpufreq_tsc);
 static struct clocksource clocksource_tsc;
 
 /*
- * We compare the TSC to the cycle_last value in the clocksource
+ * We used to compare the TSC to the cycle_last value in the clocksource
  * structure to avoid a nasty time-warp. This can be observed in a
  * very small window right after one CPU updated cycle_last under
  * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which
@@ -961,26 +960,23 @@ static struct clocksource clocksource_tsc;
  * due to the unsigned delta calculation of the time keeping core
  * code, which is necessary to support wrapping clocksources like pm
  * timer.
+ *
+ * This sanity check is now done in the core timekeeping code.
+ * checking the result of read_tsc() - cycle_last for being negative.
+ * That works because CLOCKSOURCE_MASK(64) does not mask out any bit.
  */
 static cycle_t read_tsc(struct clocksource *cs)
 {
-       cycle_t ret = (cycle_t)get_cycles();
-
-       return ret >= clocksource_tsc.cycle_last ?
-               ret : clocksource_tsc.cycle_last;
-}
-
-static void resume_tsc(struct clocksource *cs)
-{
-       if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
-               clocksource_tsc.cycle_last = 0;
+       return (cycle_t)get_cycles();
 }
 
+/*
+ * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
+ */
 static struct clocksource clocksource_tsc = {
        .name                   = "tsc",
        .rating                 = 300,
        .read                   = read_tsc,
-       .resume                 = resume_tsc,
        .mask                   = CLOCKSOURCE_MASK(64),
        .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
                                  CLOCK_SOURCE_MUST_VERIFY,