1 files changed, 15 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index d20947cf1735..9368da371f36 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -108,7 +108,7 @@ static void decrementer_set_mode(enum clock_event_mode mode,
 static struct clock_event_device decrementer_clockevent = {
        .name           = "decrementer",
        .rating         = 200,
-       .shift          = 32,
+       .shift          = 16,
        .mult           = 0,     /* To be filled in */
        .irq            = 0,
        .set_next_event = decrementer_set_next_event,
@@ -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;
 }