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.
Fixes: 1db4496f167b ("drm/amdgpu: fix power state when port pm is unavailable") Reported-and-tested-by: Mike Lothian <mike@fireburn.co.uk> Signed-off-by: Peter Wu <peter@lekensteyn.nl> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: <stable@vger.kernel.org> # 4.8+