1 files changed, 42 insertions, 22 deletions

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
index d4dae1f12d62..46033909d950 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
@@ -36,25 +36,32 @@ nvkm_timer_alarm_trigger(struct nvkm_timer *tmr)
 	unsigned long flags;
 	LIST_HEAD(exec);
 
-	/* move any due alarms off the pending list */
+	/* Process pending alarms. */
 	spin_lock_irqsave(&tmr->lock, flags);
 	list_for_each_entry_safe(alarm, atemp, &tmr->alarms, head) {
-		if (alarm->timestamp <= nvkm_timer_read(tmr))
-			list_move_tail(&alarm->head, &exec);
+		/* Have we hit the earliest alarm that hasn't gone off? */
+		if (alarm->timestamp > nvkm_timer_read(tmr)) {
+			/* Schedule it.  If we didn't race, we're done. */
+			tmr->func->alarm_init(tmr, alarm->timestamp);
+			if (alarm->timestamp > nvkm_timer_read(tmr))
+				break;
+		}
+
+		/* Move to completed list.  We'll drop the lock before
+		 * executing the callback so it can reschedule itself.
+		 */
+		list_del_init(&alarm->head);
+		list_add(&alarm->exec, &exec);
 	}
 
-	/* reschedule interrupt for next alarm time */
-	if (!list_empty(&tmr->alarms)) {
-		alarm = list_first_entry(&tmr->alarms, typeof(*alarm), head);
-		tmr->func->alarm_init(tmr, alarm->timestamp);
-	} else {
+	/* Shut down interrupt if no more pending alarms. */
+	if (list_empty(&tmr->alarms))
 		tmr->func->alarm_fini(tmr);
-	}
 	spin_unlock_irqrestore(&tmr->lock, flags);
 
-	/* execute any pending alarm handlers */
-	list_for_each_entry_safe(alarm, atemp, &exec, head) {
-		list_del_init(&alarm->head);
+	/* Execute completed callbacks. */
+	list_for_each_entry_safe(alarm, atemp, &exec, exec) {
+		list_del(&alarm->exec);
 		alarm->func(alarm);
 	}
 }
@@ -65,24 +72,37 @@ nvkm_timer_alarm(struct nvkm_timer *tmr, u32 nsec, struct nvkm_alarm *alarm)
 	struct nvkm_alarm *list;
 	unsigned long flags;
 
-	alarm->timestamp = nvkm_timer_read(tmr) + nsec;
-
-	/* append new alarm to list, in soonest-alarm-first order */
+	/* Remove alarm from pending list.
+	 *
+	 * This both protects against the corruption of the list,
+	 * and implements alarm rescheduling/cancellation.
+	 */
 	spin_lock_irqsave(&tmr->lock, flags);
-	if (!nsec) {
-		if (!list_empty(&alarm->head))
-			list_del(&alarm->head);
-	} else {
+	list_del_init(&alarm->head);
+
+	if (nsec) {
+		/* Insert into pending list, ordered earliest to latest. */
+		alarm->timestamp = nvkm_timer_read(tmr) + nsec;
 		list_for_each_entry(list, &tmr->alarms, head) {
 			if (list->timestamp > alarm->timestamp)
 				break;
 		}
+
 		list_add_tail(&alarm->head, &list->head);
+
+		/* Update HW if this is now the earliest alarm. */
+		list = list_first_entry(&tmr->alarms, typeof(*list), head);
+		if (list == alarm) {
+			tmr->func->alarm_init(tmr, alarm->timestamp);
+			/* This shouldn't happen if callers aren't stupid.
+			 *
+			 * Worst case scenario is that it'll take roughly
+			 * 4 seconds for the next alarm to trigger.
+			 */
+			WARN_ON(alarm->timestamp <= nvkm_timer_read(tmr));
+		}
 	}
 	spin_unlock_irqrestore(&tmr->lock, flags);
-
-	/* process pending alarms */
-	nvkm_timer_alarm_trigger(tmr);
 }
 
 void