From 4156e9a8ef5b521185f451213d33fa661f38512e Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 4 Sep 2008 22:47:47 +0200
Subject: x86: quick TSC calibration, improve

- make sure the final TSC timestamp is reliable too

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 839070b..6dab90f 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -317,6 +317,12 @@ static unsigned long quick_pit_calibrate(void)
 		t2 = get_cycles();
 
 		/*
+		 * Make sure we can rely on the second TSC timestamp:
+		 */
+		if (!pit_expect_msb(--expect))
+			goto failed;
+
+		/*
 		 * Ok, if we get here, then we've seen the
 		 * MSB of the PIT decrement QUICK_PIT_ITERATIONS
 		 * times, and each MSB had many hits, so we never
-- 
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