BugLink: http://bugs.launchpad.net/bugs/1638267

commit 02cfb5fc upstream.

Ported from Rex's amdgpu change.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>