drm/panthor: Fix immediate ticking on a disabled tick

We have a few paths where we schedule the tick work immediately without
changing the resched_target. If the tick was stopped, this would lead
to a remaining_jiffies that's always > 0, and it wouldn't force a full
tick in that case. Add extra checks to cover that case properly.

v2:
- Fix typo
- Simplify the code as suggested by Steve

v3:
- Collect R-b

Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Link: https://patch.msgid.link/20251128094839.3856402-6-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 531b52ee3a92..1efeabc4b0ac 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -2435,6 +2435,7 @@ static void tick_work(struct work_struct *work)
 						      tick_work.work);
 	struct panthor_device *ptdev = sched->ptdev;
 	struct panthor_sched_tick_ctx ctx;
+	u64 resched_target = sched->resched_target;
 	u64 remaining_jiffies = 0, resched_delay;
 	u64 now = get_jiffies_64();
 	int prio, ret, cookie;
@@ -2447,8 +2448,12 @@ static void tick_work(struct work_struct *work)
 	if (drm_WARN_ON(&ptdev->base, ret))
 		goto out_dev_exit;
 
-	if (time_before64(now, sched->resched_target))
-		remaining_jiffies = sched->resched_target - now;
+	/* If the tick is stopped, calculate when the next tick would be */
+	if (resched_target == U64_MAX)
+		resched_target = sched->last_tick + sched->tick_period;
+
+	if (time_before64(now, resched_target))
+		remaining_jiffies = resched_target - now;
 
 	full_tick = remaining_jiffies == 0;