[PATCH] x86-64: - Ignore long SMI interrupts in clock calibration code - update 1

Add failsafe mechanism to HPET/TSC clock calibration.

	Signed-off-by: Jack Steiner <steiner@sgi.com>
Updated to include failsafe mechanism & additional community feedback.
Patch built on latest 2.6.20-rc4-mm1 tree.

Signed-off-by: Andi Kleen <ak@suse.de>

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 335cc91c49b722c87ba12e8b4040c1f0ee38869b..9c7fba30dac1209745893cbb382c28bbcbb5baae 100644 (file)
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -657,6 +657,7 @@ core_initcall(cpufreq_tsc);
 
 #define TICK_COUNT 100000000
 #define TICK_MIN   5000
+#define MAX_READ_RETRIES 5
 
 /*
  * Some platforms take periodic SMI interrupts with 5ms duration. Make sure none
@@ -664,13 +665,17 @@ core_initcall(cpufreq_tsc);
  */
 static void __init read_hpet_tsc(int *hpet, int *tsc)
 {
-       int tsc1, tsc2, hpet1;
+       int tsc1, tsc2, hpet1, retries = 0;
+       static int msg;
 
        do {
                tsc1 = get_cycles_sync();
                hpet1 = hpet_readl(HPET_COUNTER);
                tsc2 = get_cycles_sync();
-       } while (tsc2 - tsc1 > TICK_MIN);
+       } while (tsc2 - tsc1 > TICK_MIN && retries++ < MAX_READ_RETRIES);
+       if (retries >= MAX_READ_RETRIES && !msg++)
+               printk(KERN_WARNING
+                      "hpet.c: exceeded max retries to read HPET & TSC\n");
        *hpet = hpet1;
        *tsc = tsc2;
 }