clockevents: Shutdown detached clockevent device

A clockevent device is marked DETACHED when it is replaced by another
clockevent device.

The device is shutdown properly for drivers that implement legacy
->set_mode() callback, as we call ->set_mode() for CLOCK_EVT_MODE_UNUSED
as well.

But for the new per-state callback interface, we skip shutting down the
device, as we thought its an internal state change. That wasn't correct.

The effect is that the device is left programmed in oneshot or periodic
mode.

Fall-back to 'case CLOCK_EVT_STATE_SHUTDOWN', to shutdown the device.

Fixes: bd624d75 "clockevents: Introduce mode specific callbacks"
Reported-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/eef0a91c51b74d4e52c8e5a95eca27b5a0563f07.1428650683.git.viresh.kumar@linaro.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

kernel/time/clockevents.c

@@ -117,11 +117,7 @@ static int __clockevents_set_state(struct clock_event_device *dev,
 	/* Transition with new state-specific callbacks */
 	switch (state) {
 	case CLOCK_EVT_STATE_DETACHED:
-		/*
-		 * This is an internal state, which is guaranteed to go from
-		 * SHUTDOWN to DETACHED. No driver interaction required.
-		 */
-		return 0;
+		/* The clockevent device is getting replaced. Shut it down. */
 
 	case CLOCK_EVT_STATE_SHUTDOWN:
 		return dev->set_state_shutdown(dev);