x86: restrict PIT clocksource usage

[linux-2.6-omap-h63xx.git] / arch / x86 / kernel / i8253.c

diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index a42c807453253f83fad63373567ed050a6ae1ac1..0f8f35458a8f49397430521c04a69a8cf4b6ffb0 100644 (file)
--- a/arch/x86/kernel/i8253.c
+++ b/arch/x86/kernel/i8253.c
@@ -197,7 +197,15 @@ static struct clocksource clocksource_pit = {
 
 static int __init init_pit_clocksource(void)
 {
-       if (num_possible_cpus() > 1) /* PIT does not scale! */
+        /*
+         * Several reasons not to register PIT as a clocksource:
+         *
+         * - On SMP PIT does not scale due to i8253_lock
+         * - when HPET is enabled
+         * - when local APIC timer is active (PIT is switched off)
+         */
+       if (num_possible_cpus() > 1 || is_hpet_enabled() ||
+           pit_clockevent.mode != CLOCK_EVT_MODE_PERIODIC)
                return 0;
 
        clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);