[bug report] drm/amd/display: Register DMUB service with DC

[Dan Carpenter]

Hello Nicholas Kazlauskas,

This is a semi-automatic email about new static checker warnings.

The patch 0f80e7cdc012: "drm/amd/display: Register DMUB service with 
DC" from Oct 28, 2019, leads to the following Smatch complaint:

    drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:1049 amdgpu_dm_fini()
     warn: variable dereferenced before check 'adev->dm.dc' (see line 1038)

drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c
  1029  #ifdef CONFIG_DRM_AMD_DC_HDCP
  1030          if (adev->dm.hdcp_workqueue) {
  1031                  hdcp_destroy(adev->dm.hdcp_workqueue);
  1032                  adev->dm.hdcp_workqueue = NULL;
  1033          }
  1034  
  1035          if (adev->dm.dc)
                    ^^^^^^^^^^^
Check

  1036                  dc_deinit_callbacks(adev->dm.dc);
  1037	#endif
  1038		if (adev->dm.dc->ctx->dmub_srv) {
                    ^^^^^^^^^^^^^^^^
Unchecked dereference

  1039			dc_dmub_srv_destroy(&adev->dm.dc->ctx->dmub_srv);
  1040			adev->dm.dc->ctx->dmub_srv = NULL;
  1041		}
  1042	
  1043		if (adev->dm.dmub_bo)
  1044			amdgpu_bo_free_kernel(&adev->dm.dmub_bo,
  1045					      &adev->dm.dmub_bo_gpu_addr,
  1046					      &adev->dm.dmub_bo_cpu_addr);
  1047	
  1048		/* DC Destroy TODO: Replace destroy DAL */
  1049		if (adev->dm.dc)
                    ^^^^^^^^^^^
Check

  1050			dc_destroy(&adev->dm.dc);
  1051		/*

regards,
dan carpenter