jiffies: Remove compile time assumptions about CLOCK_TICK_RATE

[~andy/linux] / kernel / time / jiffies.c

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index a470154e040826f9549e5faf9ed4aefd174de698..6629bf7b52856849899c348156b65ce3cc732cd4 100644 (file)
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -37,7 +37,7 @@
  * requested HZ value. It is also not recommended
  * for "tick-less" systems.
  */
-#define NSEC_PER_JIFFY ((u32)((((u64)NSEC_PER_SEC)<<8)/ACTHZ))
+#define NSEC_PER_JIFFY ((NSEC_PER_SEC+HZ/2)/HZ)
 
 /* Since jiffies uses a simple NSEC_PER_JIFFY multiplier
  * conversion, the .shift value could be zero. However
@@ -95,3 +95,33 @@ struct clocksource * __init __weak clocksource_default_clock(void)
 {
        return &clocksource_jiffies;
 }
+
+struct clocksource refined_jiffies;
+
+int register_refined_jiffies(long cycles_per_second)
+{
+       u64 nsec_per_tick, shift_hz;
+       long cycles_per_tick;
+
+
+
+       refined_jiffies = clocksource_jiffies;
+       refined_jiffies.name = "refined-jiffies";
+       refined_jiffies.rating++;
+
+       /* Calc cycles per tick */
+       cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
+       /* shift_hz stores hz<<8 for extra accuracy */
+       shift_hz = (u64)cycles_per_second << 8;
+       shift_hz += cycles_per_tick/2;
+       do_div(shift_hz, cycles_per_tick);
+       /* Calculate nsec_per_tick using shift_hz */
+       nsec_per_tick = (u64)NSEC_PER_SEC << 8;
+       nsec_per_tick += (u32)shift_hz/2;
+       do_div(nsec_per_tick, (u32)shift_hz);
+
+       refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
+
+       clocksource_register(&refined_jiffies);
+       return 0;
+}