/*
- * i8253.c 8253/PIT functions
+ * 8253/PIT functions
*
*/
#include <linux/clockchips.h>
* On UP the PIT can serve all of the possible timer functions. On SMP systems
* it can be solely used for the global tick.
*
- * The profiling and update capabilites are switched off once the local apic is
+ * The profiling and update capabilities are switched off once the local apic is
* registered. This mechanism replaces the previous #ifdef LOCAL_APIC -
* !using_apic_timer decisions in do_timer_interrupt_hook()
*/
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);