drm/amdgpu: disable gfxoff if VCN is busy

Toggle on/off gfxoff during video playback to fix gpu hang.

v2: change sequence to be more compatible with original code.
Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -358,6 +358,7 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work)
 	}
 
 	if (!fences && !atomic_read(&adev->vcn.total_submission_cnt)) {
+		amdgpu_gfx_off_ctrl(adev, true);
 		amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,
 		       AMD_PG_STATE_GATE);
 	} else {
@@ -370,7 +371,9 @@ void amdgpu_vcn_ring_begin_use(struct amdgpu_ring *ring)
 	struct amdgpu_device *adev = ring->adev;
 
 	atomic_inc(&adev->vcn.total_submission_cnt);
-	cancel_delayed_work_sync(&adev->vcn.idle_work);
+
+	if (!cancel_delayed_work_sync(&adev->vcn.idle_work))
+		amdgpu_gfx_off_ctrl(adev, false);
 
 	mutex_lock(&adev->vcn.vcn_pg_lock);
 	amdgpu_device_ip_set_powergating_state(adev, AMD_IP_BLOCK_TYPE_VCN,