https://bugzilla.kernel.org/show_bug.cgi?id=72701
--- Comment #8 from Alex Deucher alexdeucher@gmail.com --- (In reply to klod from comment #7)
I think those patches are applied in 3.14 and 3.13.8, but i still need to use radeon.runpm=0 in order to boot with my discrete card.
You have a PX system so those patches are not relevant for you. It seems runpm is not working properly on your system. Booting with radeon.runpm=0 reverts back to the 3.12 behavior (PX dGPUs are not dynamically powered down).