[PARISC] disable cr16 clocksource when multiple CPUs are online

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 19 insertions, 5 deletions

diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index e47e27cea42e..c33b6e0f7c47 100644
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -99,7 +99,7 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
          * cycles after the IT fires. But it's arbitrary how much time passes
          * before we call it "late". I've picked one second.
          */
-        if (ticks_elapsed > HZ) {
+        if (unlikely(ticks_elapsed > HZ)) {
                 /* Scenario 3: very long delay?  bad in any case */
                 printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
                         " cycles %lX rem %lX "
@@ -180,6 +180,8 @@ static cycle_t read_cr16(void)
         return get_cycles();
 }
 
+static int cr16_update_callback(void);
+
 static struct clocksource clocksource_cr16 = {
         .name                   = "cr16",
         .rating                 = 300,
@@ -187,9 +189,25 @@ static struct clocksource clocksource_cr16 = {
         .mask                   = CLOCKSOURCE_MASK(BITS_PER_LONG),
         .mult                   = 0, /* to be set */
         .shift                  = 22,
+        .update_callback        = cr16_update_callback,
         .is_continuous          = 1,
 };
 
+static int cr16_update_callback(void)
+{
+        int change = 0;
+
+        /* since the cr16 cycle counters are not syncronized across CPUs,
+           we'll check if we should switch to a safe clocksource: */
+        if (clocksource_cr16.rating != 0 && num_online_cpus() > 1) {
+                clocksource_cr16.rating = 0;
+                clocksource_reselect();
+                change = 1;
+        }
+
+        return change;
+}
+
 
 /*
  * XXX: We can do better than this.
@@ -225,10 +243,6 @@ void __init time_init(void)
         current_cr16_khz = PAGE0->mem_10msec/10;  /* kHz */
         clocksource_cr16.mult = clocksource_khz2mult(current_cr16_khz,
                                                 clocksource_cr16.shift);
-        /* lower the rating if we already know its unstable: */
-        if (num_online_cpus()>1)
-                clocksource_cr16.rating = 200;
-
         clocksource_register(&clocksource_cr16);
 
         if (pdc_tod_read(&tod_data) == 0) {