From: Andrew Morton <akpm@osdl.org>

Put it back in the right place.

Cc: Andi Kleen <ak@suse.de>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 arch/x86_64/kernel/hpet.c |   24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

Index: linux-2.6.20-rc6-mm/arch/x86_64/kernel/hpet.c
===================================================================
--- linux-2.6.20-rc6-mm.orig/arch/x86_64/kernel/hpet.c
+++ linux-2.6.20-rc6-mm/arch/x86_64/kernel/hpet.c
@@ -152,6 +152,24 @@ int hpet_reenable(void)
  */
 
 #define TICK_COUNT 100000000
+#define TICK_MIN   5000
+
+/*
+ * Some platforms take periodic SMI interrupts with 5ms duration. Make sure none
+ * occurs between the reads of the hpet & TSC.
+ */
+static void __init read_hpet_tsc(int *hpet, int *tsc)
+{
+	int tsc1, tsc2, hpet1;
+
+	do {
+		tsc1 = get_cycles_sync();
+		hpet1 = hpet_readl(HPET_COUNTER);
+		tsc2 = get_cycles_sync();
+	} while (tsc2 - tsc1 > TICK_MIN);
+	*hpet = hpet1;
+	*tsc = tsc2;
+}
 
 unsigned int __init hpet_calibrate_tsc(void)
 {
@@ -161,13 +179,11 @@ unsigned int __init hpet_calibrate_tsc(v
 
 	local_irq_save(flags);
 
-	hpet_start = hpet_readl(HPET_COUNTER);
-	rdtscl(tsc_start);
+	read_hpet_tsc(&hpet_start, &tsc_start);
 
 	do {
 		local_irq_disable();
-		hpet_now = hpet_readl(HPET_COUNTER);
-		tsc_now = get_cycles_sync();
+		read_hpet_tsc(&hpet_now, &tsc_now);
 		local_irq_restore(flags);
 	} while ((tsc_now - tsc_start) < TICK_COUNT &&
 		(hpet_now - hpet_start) < TICK_COUNT);