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drm/panthor: Fix race with suspend during unplug

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There is a race between panthor_device_unplug() and
panthor_device_suspend() which can lead to IRQ handlers running on a
powered down GPU. This is how it can happen:
- unplug routine calls drm_dev_unplug()
- panthor_device_suspend() can now execute, and will skip a lot of
  important work because the device is currently marked as unplugged.
- IRQs will remain active in this case and IRQ handlers can therefore
  try to access a powered down GPU.

The fix is simply to take the PM ref in panthor_device_unplug() a
little bit earlier, before drm_dev_unplug().

Signed-off-by: Ketil Johnsen <ketil.johnsen@arm.com>
Fixes: 5fe909cae1 ("drm/panthor: Add the device logical block")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251022103242.1083311-1-ketil.johnsen@arm.com
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
This commit is contained in:
Ketil Johnsen 2025-10-22 12:32:41 +02:00 committed by Liviu Dudau
parent 65c22519cf
commit 08be57e6e8
1 changed files with 2 additions and 2 deletions
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4
drivers/gpu/drm/panthor/panthor_device.c
View File

@ -84,6 +84,8 @@ void panthor_device_unplug(struct panthor_device *ptdev)
return;
}
drm_WARN_ON(&ptdev->base, pm_runtime_get_sync(ptdev->base.dev) < 0);
/* Call drm_dev_unplug() so any access to HW blocks happening after
* that point get rejected.
*/
@ -94,8 +96,6 @@ void panthor_device_unplug(struct panthor_device *ptdev)
*/
mutex_unlock(&ptdev->unplug.lock);
drm_WARN_ON(&ptdev->base, pm_runtime_get_sync(ptdev->base.dev) < 0);
/* Now, try to cleanly shutdown the GPU before the device resources
* get reclaimed.
*/