Not sure if you accept bugs in radeon/KMS code, but because it was working before (when radeon KMS in Airlied's tree was based on 2.6.27-something) and now it broke n ... just for not losing this case i will enter some details here.
01:00.0 VGA compatible controller: ATI Technologies Inc RV280 [Radeon 9200 SE] (rev 01) (prog-if 00 [VGA controller])
Subsystem: Hightech Information System Ltd. Excalibur 9200SE VIVO 128M
Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 16
Memory at c8000000 (32-bit, prefetchable) [size=128M]
I/O ports at b800 [size=256]
Memory at d7ef0000 (32-bit, non-prefetchable) [size=64K]
Expansion ROM at d7ec0000 [disabled] [size=128K]
Capabilities:  AGP version 2.0
Capabilities:  Power Management version 2
Kernel driver in use: radeon
Kernel modules: radeonfb
It works fine with current xf86-video-ati, with single VGA output connected to CRT monitor.
I have drm-rawhide tree, up to commit 5d9a97d1d81e5d0c0115e01d7a1cf7b3f72b3c0d "Author: Dave Airlie <email@example.com>
Date: Fri Apr 17 20:49:35 2009 +1000
drm: add missing helper commit"
Kernel compiles and boots fine, but if i load radeon.ko with modeset=1 parameter i got only black screen (but it doesn't saying "No signal")
Created attachment 24944 [details]
some lines from /var/log/debug
drm.ko was loaded with debug=1 of cource
Created attachment 24945 [details]
few lines from /var/log/messages
Looks like AGP working OK, guessing from "[drm] writeback test succeeded in 1 usecs" line .. I can be wrong here.
Created attachment 24946 [details]
X.org log from working userspace driver (with non-KMS drm)
Sorry, it was configuration issue. If i ran "modprobe fbcon" manually - it works.
Please attach full dmesg and output of lspci -vv
Please check the status of your issue.
Sorry, I completely forgot about it!