[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>

diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index e47e27c..c33b6e0 100644 (file)
--- 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) {