drm/amdgpu: always sending PSP messages LOAD_ASD and UNLOAD_TA

We allow sending PSP messages LOAD_ASD and UNLOAD_TA without
acquiring a lock in drm_dev_enter during driver unload
because we must call drm_dev_unplug as the beginning
of unload driver sequence.
Added WARNING if other PSP messages are sent without a lock.
After this commit, the following commands would work
 -sudo modprobe -r amdgpu
 -sudo modprobe amdgpu
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Reviewed-by Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -606,12 +606,21 @@ psp_cmd_submit_buf(struct psp_context *psp,
 	int timeout = 20000;
 	bool ras_intr = false;
 	bool skip_unsupport = false;
+	bool dev_entered;
 
 	if (psp->adev->no_hw_access)
 		return 0;
 
-	if (!drm_dev_enter(adev_to_drm(psp->adev), &idx))
-		return 0;
+	dev_entered = drm_dev_enter(adev_to_drm(psp->adev), &idx);
+	/*
+	 * We allow sending PSP messages LOAD_ASD and UNLOAD_TA without acquiring
+	 * a lock in drm_dev_enter during driver unload because we must call
+	 * drm_dev_unplug as the beginning  of unload driver sequence . It is very
+	 * crucial that userspace can't access device instances anymore.
+	 */
+	if (!dev_entered)
+		WARN_ON(psp->cmd_buf_mem->cmd_id != GFX_CMD_ID_LOAD_ASD &&
+			psp->cmd_buf_mem->cmd_id != GFX_CMD_ID_UNLOAD_TA);
 
 	memset(psp->cmd_buf_mem, 0, PSP_CMD_BUFFER_SIZE);
 
@@ -676,7 +685,8 @@ psp_cmd_submit_buf(struct psp_context *psp,
 	}
 
 exit:
-	drm_dev_exit(idx);
+	if (dev_entered)
+		drm_dev_exit(idx);
 	return ret;
 }