https://bugs.freedesktop.org/show_bug.cgi?id=73530
--- Comment #4 from Alex Deucher agd5f@yahoo.com --- (In reply to comment #2)
Created attachment 91918 [details] Linux kernel ring buffer (`dmesg`)
Please note the Linux kernel command line, which has `radeon.modeset=0`, `drm.debug=14` and `acpi_osi=Linux`. Later the the Radeon module is removed with `sudo modprobe -r radeon` and reloaded with `sudo modprobe radeon modeset=1`.
I don't seen any radeon messages. It doesn't look like it loaded properly.