[PATCH] tick: check if broadcast device could really be stopped

[Benjamin Gaignard]

If the CPU isn't able to go in states where the clock event will
be stopped we can ignore CLOCK_EVT_FEAT_C3STOP flag.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
---
 kernel/time/tick-broadcast.c |  6 +++---
 kernel/time/tick-common.c    |  4 ++--
 kernel/time/tick-internal.h  | 12 ++++++++++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index e51778c312f1..5393778d7703 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -78,7 +78,7 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev,
 {
 	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
 	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
-	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
+	    tick_broadcast_could_stop(newdev))
 		return false;
 
 	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
@@ -188,7 +188,7 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 		 * Clear the broadcast bit for this cpu if the
 		 * device is not power state affected.
 		 */
-		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+		if (!tick_broadcast_could_stop(dev))
 			cpumask_clear_cpu(cpu, tick_broadcast_mask);
 		else
 			tick_device_setup_broadcast_func(dev);
@@ -368,7 +368,7 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 	/*
 	 * Is the device not affected by the powerstate ?
 	 */
-	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
+	if (!dev || !tick_broadcast_could_stop(dev))
 		goto out;
 
 	if (!tick_device_is_functional(dev))
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 59225b484e4e..a300ee941c56 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -72,7 +72,7 @@ int tick_is_oneshot_available(void)
 
 	if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 		return 0;
-	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+	if (!tick_broadcast_could_stop(dev))
 		return 1;
 	return tick_broadcast_oneshot_available();
 }
@@ -393,7 +393,7 @@ int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 {
 	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 
-	if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
+	if (!tick_broadcast_could_stop(td->evtdev))
 		return 0;
 
 	return __tick_broadcast_oneshot_control(state);
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 7b2496136729..99aa7b5a8dae 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -2,6 +2,7 @@
 /*
  * tick internal variable and functions used by low/high res code
  */
+#include <linux/cpuidle.h>
 #include <linux/hrtimer.h>
 #include <linux/tick.h>
 
@@ -48,6 +49,17 @@ static inline void clockevent_set_state(struct clock_event_device *dev,
 	dev->state_use_accessors = state;
 }
 
+/**
+ * Return true if the cpu could go in states where the device will be stopped
+ */
+static inline int tick_broadcast_could_stop(struct clock_event_device *dev)
+{
+	struct cpuidle_driver *drv = cpuidle_get_driver();
+
+	return !!((dev->features & CLOCK_EVT_FEAT_C3STOP)
+		  && drv && drv->bctimer);
+}
+
 extern void clockevents_shutdown(struct clock_event_device *dev);
 extern void clockevents_exchange_device(struct clock_event_device *old,
 					struct clock_event_device *new);
-- 
2.15.0