https://bugs.freedesktop.org/show_bug.cgi?id=82473
--- Comment #8 from Alex Deucher agd5f@yahoo.com --- (In reply to comment #7)
This has never worked. The HW works fine with older kernels and proprietary drivers. Tried with VGA connector, and with with the radeon.audio=0 without change in the behavior.
Which older kernels worked? Can you bisect?