clocksource: Add clocksource_register_hz/khz interface

[safe/jmp/linux-2.6] / kernel / time / clocksource.c

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 1f5dde6..f08e99c 100644 (file)
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -625,6 +625,54 @@ static void clocksource_enqueue(struct clocksource *cs)
        list_add(&cs->list, entry);
 }
 
+
+/*
+ * Maximum time we expect to go between ticks. This includes idle
+ * tickless time. It provides the trade off between selecting a
+ * mult/shift pair that is very precise but can only handle a short
+ * period of time, vs. a mult/shift pair that can handle long periods
+ * of time but isn't as precise.
+ *
+ * This is a subsystem constant, and actual hardware limitations
+ * may override it (ie: clocksources that wrap every 3 seconds).
+ */
+#define MAX_UPDATE_LENGTH 5 /* Seconds */
+
+/**
+ * __clocksource_register_scale - Used to install new clocksources
+ * @t:         clocksource to be registered
+ * @scale:     Scale factor multiplied against freq to get clocksource hz
+ * @freq:      clocksource frequency (cycles per second) divided by scale
+ *
+ * Returns -EBUSY if registration fails, zero otherwise.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * clocksource_register_hz() or clocksource_register_khz helper functions.
+ */
+int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+
+       /*
+        * Ideally we want to use  some of the limits used in
+        * clocksource_max_deferment, to provide a more informed
+        * MAX_UPDATE_LENGTH. But for now this just gets the
+        * register interface working properly.
+        */
+       clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+                                     NSEC_PER_SEC/scale,
+                                     MAX_UPDATE_LENGTH*scale);
+       cs->max_idle_ns = clocksource_max_deferment(cs);
+
+       mutex_lock(&clocksource_mutex);
+       clocksource_enqueue(cs);
+       clocksource_select();
+       clocksource_enqueue_watchdog(cs);
+       mutex_unlock(&clocksource_mutex);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(__clocksource_register_scale);
+
+
 /**
  * clocksource_register - Used to install new clocksources
  * @t:         clocksource to be registered