https://bugs.freedesktop.org/show_bug.cgi?id=46711
--- Comment #6 from Tvrtko Ursulin tvrtko.ursulin@onelan.co.uk 2012-04-16 08:00:52 PDT --- (In reply to comment #5)
(In reply to comment #4)
forcing DPMS off and on will restore display. (I have this shell script bound to F12 and taping that key will restore the display.)
xset dpms force off sleep 1 xset dpms force on
This works for me as well.
Are you getting proper hotplug connect/disconnect interrupts? The driver does exactly the same thing on hotplug interrupts. Assuming the display is active, on disconnect it calls dpms off, on connect it calls dpms on. It also sends an event to userspace so it's possible that may be causing a conflict. Take a look at radeon_connector_hotplug() in radeon_connectors.c in the kernel.
I see it calling drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON) from radeon_connector_hotplug when I plug in the cable, meaning HPD sense said there is something connected.
How to investigate this potential conflict with userspace?
Because, as I originally wrote, without X running monitor comes back fine.