2 files changed, 53 insertions, 0 deletions

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 9466eebc8e19..80acc79e0dc5 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -69,6 +69,8 @@ enum clock_event_nofitiers {
  * @retries:            number of forced programming retries
  * @set_mode:           set mode function
  * @broadcast:          function to broadcast events
+ * @min_delta_ticks:    minimum delta value in ticks stored for reconfiguration
+ * @max_delta_ticks:    maximum delta value in ticks stored for reconfiguration
  * @name:               ptr to clock event name
  * @rating:             variable to rate clock event devices
  * @irq:                IRQ number (only for non CPU local devices)
@@ -91,6 +93,9 @@ struct clock_event_device {
         void                    (*broadcast)(const struct cpumask *mask);
         void                    (*set_mode)(enum clock_event_mode mode,
                                             struct clock_event_device *);
+        unsigned long           min_delta_ticks;
+        unsigned long           max_delta_ticks;
+
         const char              *name;
         int                     rating;
         int                     irq;
@@ -123,6 +128,10 @@ extern u64 clockevent_delta2ns(unsigned long latch,
                                struct clock_event_device *evt);
 extern void clockevents_register_device(struct clock_event_device *dev);
 
+extern void clockevents_config_and_register(struct clock_event_device *dev,
+                                            u32 freq, unsigned long min_delta,
+                                            unsigned long max_delta);
+
 extern void clockevents_exchange_device(struct clock_event_device *old,
                                         struct clock_event_device *new);
 extern void clockevents_set_mode(struct clock_event_device *dev,
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 0d74b9ba90c8..c69e88c94446 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -194,6 +194,50 @@ 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);
+}
+
 /*
  * Noop handler when we shut down an event device
  */