drm/nouveau/tmr: avoid processing completed alarms when adding a new one

The idea here was to avoid having to "manually" program the HW if there's
a new earliest alarm.  This was lazy and bad, as it leads to loads of fun
races between inter-related callers (ie. therm).

Turns out, it's not so difficult after all.  Go figure ;)

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
index d898787d514ca9ab83672793eeb227d43f272fdd..f2a86eae0a0d624b31cb8ee9a65e6487705a6c1a 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
@@ -86,12 +86,22 @@ nvkm_timer_alarm(struct nvkm_timer *tmr, u32 nsec, struct nvkm_alarm *alarm)
                        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