[PATCH] clockevents: return error from tick_broadcast_oneshot_control if !GENERIC_CLOCKEVENTS_BROADCAST

[Sudeep Holla]

tick_broadcast_enter returns 0 when CPU can switch to broadcast
timer and non-zero otherwise. However when GENERIC_CLOCKEVENTS_BROADCAST
and TICK_ONESHOT are disabled, tick_broadcast_oneshot_control returns 0
which indicates to the CPUIdle framework that the CPU can enter deeper
idle states even when the CPU local timer will be shutdown. If the
target state needs broadcast but not broadcast timer is available, then
the CPU can not resume back from that idle state.

This patch returns error when there's no broadcast timer support
available so that CPUIdle framework prevents the CPU from entering any
idle states losing the local timer.

Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reported-and-Tested-by: Suzuki Poulose <Suzuki.Poulose@xxxxxxx>
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
 include/linux/tick.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 3741ba1a652c..0624968a0bcc 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -70,7 +70,10 @@ static inline void tick_broadcast_control(enum tick_broadcast_mode mode) { }
 #if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT)
 extern int tick_broadcast_oneshot_control(enum tick_broadcast_state state);
 #else
-static inline int tick_broadcast_oneshot_control(enum tick_broadcast_state state) { return 0; }
+static inline int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	return -ENODEV;
+}
 #endif
 
 static inline void tick_broadcast_enable(void)
-- 
1.9.1

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