x86: quick TSC calibration, improve

- make sure the final TSC timestamp is reliable too Signed-off-by: Ingo Molnar <mingo@elte.hu>
git-mirror · Sep 4, 2008 · 4156e9a · 4156e9a
1 parent 6ac40ed
commit 4156e9a
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
@@ -316,6 +316,12 @@ 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