1 files changed, 83 insertions, 3 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index bb64beb301d9..dc1393e7cbfb 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -888,7 +888,82 @@ __cpuinit int unsynchronized_tsc(void)
         return 0;
 }
 
-static void __init init_tsc_clocksource(void)
+
+static void tsc_refine_calibration_work(struct work_struct *work);
+static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
+/**
+ * tsc_refine_calibration_work - Further refine tsc freq calibration
+ * @work - ignored.
+ *
+ * This functions uses delayed work over a period of a
+ * second to further refine the TSC freq value. Since this is
+ * timer based, instead of loop based, we don't block the boot
+ * process while this longer calibration is done.
+ *
+ * If there are any calibration anomolies (too many SMIs, etc),
+ * or the refined calibration is off by 1% of the fast early
+ * calibration, we throw out the new calibration and use the
+ * early calibration.
+ */
+static void tsc_refine_calibration_work(struct work_struct *work)
+{
+        static u64 tsc_start = -1, ref_start;
+        static int hpet;
+        u64 tsc_stop, ref_stop, delta;
+        unsigned long freq;
+
+        /* Don't bother refining TSC on unstable systems */
+        if (check_tsc_unstable())
+                goto out;
+
+        /*
+         * Since the work is started early in boot, we may be
+         * delayed the first time we expire. So set the workqueue
+         * again once we know timers are working.
+         */
+        if (tsc_start == -1) {
+                /*
+                 * Only set hpet once, to avoid mixing hardware
+                 * if the hpet becomes enabled later.
+                 */
+                hpet = is_hpet_enabled();
+                schedule_delayed_work(&tsc_irqwork, HZ);
+                tsc_start = tsc_read_refs(&ref_start, hpet);
+                return;
+        }
+
+        tsc_stop = tsc_read_refs(&ref_stop, hpet);
+
+        /* hpet or pmtimer available ? */
+        if (!hpet && !ref_start && !ref_stop)
+                goto out;
+
+        /* Check, whether the sampling was disturbed by an SMI */
+        if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
+                goto out;
+
+        delta = tsc_stop - tsc_start;
+        delta *= 1000000LL;
+        if (hpet)
+                freq = calc_hpet_ref(delta, ref_start, ref_stop);
+        else
+                freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
+
+        /* Make sure we're within 1% */
+        if (abs(tsc_khz - freq) > tsc_khz/100)
+                goto out;
+
+        tsc_khz = freq;
+        printk(KERN_INFO "Refined TSC clocksource calibration: "
+                "%lu.%03lu MHz.\n", (unsigned long)tsc_khz / 1000,
+                                        (unsigned long)tsc_khz % 1000);
+
+out:
+        clocksource_register_khz(&clocksource_tsc, tsc_khz);
+}
+
+
+static int __init init_tsc_clocksource(void)
 {
         if (tsc_clocksource_reliable)
                 clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
@@ -897,8 +972,14 @@ static void __init init_tsc_clocksource(void)
                 clocksource_tsc.rating = 0;
                 clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
         }
-        clocksource_register_khz(&clocksource_tsc, tsc_khz);
+        schedule_delayed_work(&tsc_irqwork, 0);
+        return 0;
 }
+/*
+ * We use device_initcall here, to ensure we run after the hpet
+ * is fully initialized, which may occur at fs_initcall time.
+ */
+device_initcall(init_tsc_clocksource);
 
 void __init tsc_init(void)
 {
@@ -952,6 +1033,5 @@ void __init tsc_init(void)
                 mark_tsc_unstable("TSCs unsynchronized");
 
         check_system_tsc_reliable();
-        init_tsc_clocksource();
 }