clockevents: introduce force broadcast notifier

The 64bit SMP bootup is slightly different to the 32bit one. It enables
the boot CPU local APIC timer before all CPUs are brought up. Some AMD C1E
systems have the C1E feature flag only set in the secondary CPU. Due to
the early enable of the boot CPU local APIC timer the APIC timer is
registered as a fully functional device. When we detect the wreckage during
the bringup of the secondary CPU, we need to force the boot CPU into
broadcast mode. 

Add a new notifier reason and implement the force broadcast in the clock
events layer.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/clockchips.h

@@ -31,6 +31,7 @@ enum clock_event_nofitiers {
 	CLOCK_EVT_NOTIFY_ADD,
 	CLOCK_EVT_NOTIFY_BROADCAST_ON,
 	CLOCK_EVT_NOTIFY_BROADCAST_OFF,
+	CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
 	CLOCK_EVT_NOTIFY_BROADCAST_ENTER,
 	CLOCK_EVT_NOTIFY_BROADCAST_EXIT,
 	CLOCK_EVT_NOTIFY_SUSPEND,

kernel/time/tick-broadcast.c

@@ -217,26 +217,43 @@ static void tick_do_broadcast_on_off(void *why)
 	bc = tick_broadcast_device.evtdev;
 
 	/*
-	 * Is the device in broadcast mode forever or is it not
-	 * affected by the powerstate ?
+	 * Is the device not affected by the powerstate ?
 	 */
-	if (!dev || !tick_device_is_functional(dev) ||
-	    !(dev->features & CLOCK_EVT_FEAT_C3STOP))
+	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 		goto out;
 
-	if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
+	/*
+	 * Defect device ?
+	 */
+	if (!tick_device_is_functional(dev)) {
+		/*
+		 * AMD C1E wreckage fixup:
+		 *
+		 * Device was registered functional in the first
+		 * place. Now the secondary CPU detected the C1E
+		 * misfeature and notifies us to fix it up
+		 */
+		if (*reason != CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
+			goto out;
+	}
+
+	switch (*reason) {
+	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
+	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 		if (!cpu_isset(cpu, tick_broadcast_mask)) {
 			cpu_set(cpu, tick_broadcast_mask);
 			if (td->mode == TICKDEV_MODE_PERIODIC)
 				clockevents_set_mode(dev,
 						     CLOCK_EVT_MODE_SHUTDOWN);
 		}
-	} else {
+		break;
+	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 		if (cpu_isset(cpu, tick_broadcast_mask)) {
 			cpu_clear(cpu, tick_broadcast_mask);
 			if (td->mode == TICKDEV_MODE_PERIODIC)
 				tick_setup_periodic(dev, 0);
 		}
+		break;
 	}
 
 	if (cpus_empty(tick_broadcast_mask))

kernel/time/tick-common.c

@@ -345,6 +345,7 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason,
 
 	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
+	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 		tick_broadcast_on_off(reason, dev);
 		break;