Black Screen With Xorg fglrx

[Toni Lähdekorpi]

I've got a iMac with ATI Radeon HD 4670 running Ubuntu 12.04 (also tried 11.10, same results).
Opensource driver works relatively well, except that Unity 3D is almost completely unusable and buggy.

Tried both, the installer from AMD and fglrx from jockey, the behavior is the same.
I installed the latest Catalyst driver, rebooted and got a black screen.
Trying to switch to a TTY console after trying to start Xorg doesn't work.
I need a reboot each time to test.

From xorg.log:
[ 245.672] (EE) fglrx(0): Output LVDS enabled but has no modes
[ 245.672] (EE) fglrx(0): Display Infrastructure Failed
[ 245.672] (EE) fglrx(0): PreInit failed
[ 245.672] (II) fglrx(0): === [xdl_xs111_atiddxPreInit] === end

Full log: http://pastebin.com/ppkSFB70

[Toni Lähdekorpi (lahdekorpi)]

Also on cchtml: http://ati.cchtml.com/show_bug.cgi?id=447

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Peter T Hayward (energonic)]

I use iMac 21.5" (mid 2010).
I have exactly the same problem with quantal build 12.10. I can boot into text. I can build the fglrx driver against the 3.4 kernel, on today's update.
If I let X use flgrx then I get a black screen (suspect this is a regression of the same KMS problem - choosing the wrong display port on this mac - that afflicted 12.04).
If I edit xorg.conf to use 'fbdev' then I get a desktop -so that's my workround for the moment.