Commit 08be57e6 authored by Ketil Johnsen's avatar Ketil Johnsen Committed by Liviu Dudau
Browse files

drm/panthor: Fix race with suspend during unplug 



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: default avatarKetil Johnsen <ketil.johnsen@arm.com>
Fixes: 5fe909ca ("drm/panthor: Add the device logical block")
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251022103242.1083311-1-ketil.johnsen@arm.com


Signed-off-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
parent 65c22519

drivers/gpu/drm/panthor/panthor_device.c

+2 −2
Original line number Diff line number Diff line
@@ -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.

	 */