drm/amdgpu: Fix hang on device removal.

If removing while commands in flight you cannot wait to flush the
HW fences on a ring since the device is gone.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210512142648.666476-13-andrey.grodzovsky@amd.com

drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c

@@ -36,6 +36,7 @@
 #include <linux/firmware.h>
 #include <linux/pm_runtime.h>
 
+#include <drm/drm_drv.h>
 #include "amdgpu.h"
 #include "amdgpu_trace.h"
 
@@ -525,8 +526,7 @@ int amdgpu_fence_driver_init(struct amdgpu_device *adev)
  */
 void amdgpu_fence_driver_fini_hw(struct amdgpu_device *adev)
 {
-	unsigned i, j;
-	int r;
+	int i, r;
 
 	for (i = 0; i < AMDGPU_MAX_RINGS; i++) {
 		struct amdgpu_ring *ring = adev->rings[i];
@@ -535,11 +535,15 @@ void amdgpu_fence_driver_fini_hw(struct amdgpu_device *adev)
 			continue;
 		if (!ring->no_scheduler)
 			drm_sched_fini(&ring->sched);
+		/* You can't wait for HW to signal if it's gone */
+		if (!drm_dev_is_unplugged(&adev->ddev))
 			r = amdgpu_fence_wait_empty(ring);
-		if (r) {
+		else
+			r = -ENODEV;
 		/* no need to trigger GPU reset as we are unloading */
+		if (r)
 			amdgpu_fence_driver_force_completion(ring);
-		}
+
 		if (ring->fence_drv.irq_src)
 			amdgpu_irq_put(adev, ring->fence_drv.irq_src,
 				       ring->fence_drv.irq_type);