[PATCH 6.18 171/641] drm/panthor: Fix immediate ticking on a disabled tick

Greg Kroah-Hartman
2026-02-25T01:45:02Z

6.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: Boris Brezillon <boris.brezillon@collabora.com>

[ Upstream commit 4356d21994f4ff5c87305b874939b359f16f6677 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/panthor/panthor_sched.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 03062169b8d33..3d4ac73999825 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -2374,6 +2374,7 @@ 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;
@@ -2386,8 +2387,12 @@ 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;

--
2.51.0