It works ootb with any of the more recent distros, some even with KMS. According to lsmod (dunno is that how you do it?) they are using the radeon driver. Fedora, Gentoo, Arch , Ubuntu all display the native resolution without tweaking xorg.conf or something like that. I don't know whether that's because Xorg, kernel or another part in Debian doesn't support my hardware yet or it's because of some misconfiguration.
Following the wiki "ATIProprietary" [1] and using fglrx does work but I want to use the open source drivers. I followed the "AtiHowTo" [2]. The default kernel seems to be configured correctly (see the paragraph "configuring the kernel"). But when I edit xorg.conf and add the 'Driver "radeon"' xorg fails to start.
Suppose the relevant part of the log file is:
(II) Primary Device is: PCI 01:05:0
(--) Assigning device section with no busID to primary device
(EE) No devices detected.
Fatal server error:
no screens found
Maybe I did miss something obvious, here's all I I did:
fresh install from netiso, minimal cli installation; apt-get install xorg, startx > wrong resolution. Exit xorg, edit /etc/X11/xorg.conf and added the radeon driver to the "Device" section, startx again, xorg fails. Replacing it with radeonhd gives the same error. The only driver xorg.conf accepts is vesa.
This is my first post to the debian mailing list. If I violated some policy or blundered otherwise, my apologies and feel free to correct me.
[1] ...
http://wiki.debian.org/ATIProprietary
[2] ...
http://wiki.debian.org/AtiHowTo