[PATCH 6.19 193/781] drm/panthor: Recover from panthor_gpu_flush_caches() failures

Greg Kroah-Hartman
2026-02-25T01:30:28Z

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

[ Upstream commit 3c0a60195b37af83bbbaf223cd3a78945bace49e ]

We have seen a few cases where the whole memory subsystem is blocked
and flush operations never complete. When that happens, we want to:

- schedule a reset, so we can recover from this situation
- in the reset path, we need to reset the pending_reqs so we can send
new commands after the reset
- if more panthor_gpu_flush_caches() operations are queued after
the timeout, we skip them and return -EIO directly to avoid needless
waits (the memory block won't miraculously work again)

Note that we drop the WARN_ON()s because these hangs can be triggered
with buggy GPU jobs created by the UMD, and there's no way we can
prevent it. We do keep the error messages though.

v2:
- New patch

v3:
- Collect R-b
- Explicitly mention the fact we dropped the WARN_ON()s in the commit
message

v4:
- No changes

Fixes: 5cd894e258c4 ("drm/panthor: Add the GPU logical block")
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251128084841.3804658-4-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_gpu.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
index 06b231b2460ab..9cb5dee932120 100644
--- a/drivers/gpu/drm/panthor/panthor_gpu.c
+++ b/drivers/gpu/drm/panthor/panthor_gpu.c
@@ -289,38 +289,42 @@ int panthor_gpu_l2_power_on(struct panthor_device *ptdev)
int panthor_gpu_flush_caches(struct panthor_device *ptdev,
u32 l2, u32 lsc, u32 other)
{
- bool timedout = false;
unsigned long flags;
+ int ret = 0;

/* Serialize cache flush operations. */
guard(mutex)(&ptdev->gpu->cache_flush_lock);

spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
- if (!drm_WARN_ON(&ptdev->base,
- ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED)) {
+ if (!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED)) {
ptdev->gpu->pending_reqs |= GPU_IRQ_CLEAN_CACHES_COMPLETED;
gpu_write(ptdev, GPU_CMD, GPU_FLUSH_CACHES(l2, lsc, other));
+ } else {
+ ret = -EIO;
}
spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);

+ if (ret)
+ return ret;
+
if (!wait_event_timeout(ptdev->gpu->reqs_acked,
!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED),
msecs_to_jiffies(100))) {
spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
if ((ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED) != 0 &&
!(gpu_read(ptdev, GPU_INT_RAWSTAT) & GPU_IRQ_CLEAN_CACHES_COMPLETED))
- timedout = true;
+ ret = -ETIMEDOUT;
else
ptdev->gpu->pending_reqs &= ~GPU_IRQ_CLEAN_CACHES_COMPLETED;
spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
}

- if (timedout) {
+ if (ret) {
+ panthor_device_schedule_reset(ptdev);
drm_err(&ptdev->base, "Flush caches timeout");
- return -ETIMEDOUT;
}

- return 0;
+ return ret;
}

/**
@@ -360,6 +364,7 @@ int panthor_gpu_soft_reset(struct panthor_device *ptdev)
return -ETIMEDOUT;
}

+ ptdev->gpu->pending_reqs = 0;
return 0;
}

--
2.51.0