Merge branch 'timers-clockevents-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-clockevents-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86: hpet: Cleanup the clockevents init and register code
  x86: Convert PIT to clockevents_config_and_register()
  clockevents: Provide interface to reconfigure an active clock event device
  clockevents: Provide combined configure and register function
  clockevents: Restructure clock_event_device members
  clocksource: Get rid of the hardcoded 5 seconds sleep time limit
  clocksource: Restructure clocksource struct members

2 files changed, 83 insertions, 19 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 0d74b9ba90c8..22a9da9a9c96 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -194,6 +194,70 @@ void clockevents_register_device(struct clock_event_device *dev)
 }
 EXPORT_SYMBOL_GPL(clockevents_register_device);
 
+static void clockevents_config(struct clock_event_device *dev,
+                               u32 freq)
+{
+        unsigned long sec;
+
+        if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+                return;
+
+        /*
+         * Calculate the maximum number of seconds we can sleep. Limit
+         * to 10 minutes for hardware which can program more than
+         * 32bit ticks so we still get reasonable conversion values.
+         */
+        sec = dev->max_delta_ticks;
+        do_div(sec, freq);
+        if (!sec)
+                sec = 1;
+        else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
+                sec = 600;
+
+        clockevents_calc_mult_shift(dev, freq, sec);
+        dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
+        dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
+}
+
+/**
+ * clockevents_config_and_register - Configure and register a clock event device
+ * @dev:        device to register
+ * @freq:       The clock frequency
+ * @min_delta:  The minimum clock ticks to program in oneshot mode
+ * @max_delta:  The maximum clock ticks to program in oneshot mode
+ *
+ * min/max_delta can be 0 for devices which do not support oneshot mode.
+ */
+void clockevents_config_and_register(struct clock_event_device *dev,
+                                     u32 freq, unsigned long min_delta,
+                                     unsigned long max_delta)
+{
+        dev->min_delta_ticks = min_delta;
+        dev->max_delta_ticks = max_delta;
+        clockevents_config(dev, freq);
+        clockevents_register_device(dev);
+}
+
+/**
+ * clockevents_update_freq - Update frequency and reprogram a clock event device.
+ * @dev:        device to modify
+ * @freq:       new device frequency
+ *
+ * Reconfigure and reprogram a clock event device in oneshot
+ * mode. Must be called on the cpu for which the device delivers per
+ * cpu timer events with interrupts disabled!  Returns 0 on success,
+ * -ETIME when the event is in the past.
+ */
+int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
+{
+        clockevents_config(dev, freq);
+
+        if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
+                return 0;
+
+        return clockevents_program_event(dev, dev->next_event, ktime_get());
+}
+
 /*
  * Noop handler when we shut down an event device
  */
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 0e17c10f8a9d..d9d5f8c885f6 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -626,19 +626,6 @@ 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_updatefreq_scale - Used update clocksource with new freq
  * @t:          clocksource to be registered
@@ -652,15 +639,28 @@ static void clocksource_enqueue(struct clocksource *cs)
  */
 void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
 {
+        unsigned long sec;
+
         /*
-         * 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.
+         * Calc the maximum number of seconds which we can run before
+         * wrapping around. For clocksources which have a mask > 32bit
+         * we need to limit the max sleep time to have a good
+         * conversion precision. 10 minutes is still a reasonable
+         * amount. That results in a shift value of 24 for a
+         * clocksource with mask >= 40bit and f >= 4GHz. That maps to
+         * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
+         * margin as we do in clocksource_max_deferment()
          */
+        sec = (cs->mask - (cs->mask >> 5));
+        do_div(sec, freq);
+        do_div(sec, scale);
+        if (!sec)
+                sec = 1;
+        else if (sec > 600 && cs->mask > UINT_MAX)
+                sec = 600;
+
         clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
-                                      NSEC_PER_SEC/scale,
-                                      MAX_UPDATE_LENGTH*scale);
+                               NSEC_PER_SEC / scale, sec * scale);
         cs->max_idle_ns = clocksource_max_deferment(cs);
 }
 EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);