1 files changed, 38 insertions, 0 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index ce8e50239332..d632934cb638 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -626,6 +626,44 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
         local_irq_restore(flags);
 }
 
+static unsigned long long cyc2ns_suspend;
+
+void save_sched_clock_state(void)
+{
+        if (!sched_clock_stable)
+                return;
+
+        cyc2ns_suspend = sched_clock();
+}
+
+/*
+ * Even on processors with invariant TSC, TSC gets reset in some the
+ * ACPI system sleep states. And in some systems BIOS seem to reinit TSC to
+ * arbitrary value (still sync'd across cpu's) during resume from such sleep
+ * states. To cope up with this, recompute the cyc2ns_offset for each cpu so
+ * that sched_clock() continues from the point where it was left off during
+ * suspend.
+ */
+void restore_sched_clock_state(void)
+{
+        unsigned long long offset;
+        unsigned long flags;
+        int cpu;
+
+        if (!sched_clock_stable)
+                return;
+
+        local_irq_save(flags);
+
+        get_cpu_var(cyc2ns_offset) = 0;
+        offset = cyc2ns_suspend - sched_clock();
+
+        for_each_possible_cpu(cpu)
+                per_cpu(cyc2ns_offset, cpu) = offset;
+
+        local_irq_restore(flags);
+}
+
 #ifdef CONFIG_CPU_FREQ
 
 /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency