drm/amd/display: Debug-print reason for mode validation failure

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2839,10 +2839,11 @@ int amdgpu_dm_connector_mode_valid(struct drm_connector *connector,
 	if (dc_result == DC_OK)
 		result = MODE_OK;
 	else
-		DRM_DEBUG_KMS("Mode %dx%d (clk %d) failed DC validation\n",
+		DRM_DEBUG_KMS("Mode %dx%d (clk %d) failed DC validation with error %d\n",
 			      mode->vdisplay,
 			      mode->hdisplay,
-			      mode->clock);
+			      mode->clock,
+			      dc_result);
 
 	dc_stream_release(stream);