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Subject[PATCH 6/7] x86 tsc clock: implement clock latch
Date
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/kernel/tsc.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 6ff4924..c75e9f9 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -766,10 +766,28 @@ static cycle_t read_tsc(struct clocksource *cs)
ret : clocksource_tsc.cycle_last;
}

+static cycle_t read_tsc_latch(struct clocksource *cs, int index)
+{
+ cycle_t ret = (cycle_t)get_cycles();
+
+ return ret >= clocksource_tsc.cycle_last_latch[index] ?
+ ret : clocksource_tsc.cycle_last_latch[index];
+}
+
+static void update_tsc_latch(struct clocksource *cs, int oldindex,
+ int newindex)
+{
+ clocksource_tsc.cycle_last_latch[newindex] =
+ clocksource_tsc.cycle_last_latch[oldindex];
+}
+
static void resume_tsc(struct clocksource *cs)
{
- if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
+ if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3)) {
clocksource_tsc.cycle_last = 0;
+ clocksource_tsc.cycle_last_latch[0] = 0;
+ clocksource_tsc.cycle_last_latch[1] = 0;
+ }
}

static struct clocksource clocksource_tsc = {
@@ -783,6 +801,8 @@ static struct clocksource clocksource_tsc = {
#ifdef CONFIG_X86_64
.archdata = { .vclock_mode = VCLOCK_TSC },
#endif
+ .read_latch = read_tsc_latch,
+ .update_latch = update_tsc_latch,
};

void mark_tsc_unstable(char *reason)
--
1.7.10.4


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