[POWERPC] Prevent decrementer clockevents from firing early

[powerpc.git] / arch / powerpc / kernel / time.c

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index d20947c..64b503c 100644 (file)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -118,6 +118,7 @@ static struct clock_event_device decrementer_clockevent = {
 
 static DEFINE_PER_CPU(struct clock_event_device, decrementers);
 void init_decrementer_clockevent(void);
+static DEFINE_PER_CPU(u64, decrementer_next_tb);
 
 #ifdef CONFIG_PPC_ISERIES
 static unsigned long __initdata iSeries_recal_titan;
@@ -541,6 +542,7 @@ void timer_interrupt(struct pt_regs * regs)
        struct pt_regs *old_regs;
        int cpu = smp_processor_id();
        struct clock_event_device *evt = &per_cpu(decrementers, cpu);
+       u64 now;
 
        /* Ensure a positive value is written to the decrementer, or else
         * some CPUs will continuue to take decrementer exceptions */
@@ -551,6 +553,14 @@ void timer_interrupt(struct pt_regs * regs)
                do_IRQ(regs);
 #endif
 
+       now = get_tb_or_rtc();
+       if (now < per_cpu(decrementer_next_tb, cpu)) {
+               /* not time for this event yet */
+               now = per_cpu(decrementer_next_tb, cpu) - now;
+               if (now <= DECREMENTER_MAX)
+                       set_dec((unsigned int)now - 1);
+               return;
+       }
        old_regs = set_irq_regs(regs);
        irq_enter();
 
@@ -797,6 +807,10 @@ void __init clocksource_init(void)
 static int decrementer_set_next_event(unsigned long evt,
                                      struct clock_event_device *dev)
 {
+       __get_cpu_var(decrementer_next_tb) = get_tb_or_rtc() + evt;
+       /* The decrementer interrupts on the 0 -> -1 transition */
+       if (evt)
+               --evt;
        set_dec(evt);
        return 0;
 }