The ATPX method does not always exist on the dGPU, it may be located at the iGPU. The parent device of the iGPU is the root port for which bridge_d3 is false. This accidentally enables the legacy PM method which conflicts with port PM and prevented the dGPU from powering on. Ported from amdgpu commit: drm/amdgpu: fix check for port PM availability from Peter Wu. Fixes: d3ac31f3b4bf9fad (drm/radeon: fix power state when port pm is unavailable (v2)) Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: Peter Wu <peter@lekensteyn.nl> Cc: <stable@vger.kernel.org> # 4.8+