Commit 3c0a6019 authored by Boris Brezillon's avatar Boris Brezillon
Browse files

drm/panthor: Recover from panthor_gpu_flush_caches() failures 



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: 5cd894e2 ("drm/panthor: Add the GPU logical block")
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251128084841.3804658-4-boris.brezillon@collabora.com


Signed-off-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
parent 151df689

drivers/gpu/drm/panthor/panthor_gpu.c

+12 −7
Original line number Diff line number Diff line
@@ -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;

}