Bug#523589: xserver-xorg-video-radeon: dualhead broke with upgrade

[Alex Deucher]

On 4/11/09, di dit <didit21 at gmail.com> wrote:
> Package: xserver-xorg-video-radeon
>  Version: 1:6.12.2-1
>  Severity: normal
>
>  The dualhead setup I've been using for more than 6 months broke up with
>  the last upgrade. The two identical monitors work fine in clone mode but
>  the following command results in a black screen on DVI-1 (the monitor
>  goes to standby mode it seems) while the display on DVI-0 is changed as
>  expected.
>   xrandr --output DVI-1 --left-of DVI-0
>  At this stage, switching to the console (CTRL+ALT+F1) behave as expected
>  (both monitors display the same text) but switching back to X11
>  (CTRL+ALT+F7) restores the same situation (i.e. DVI-1 is black and DVI-0
>  displays the right half of the background image).
>
>  I had no success tweaking xorg.conf to get the dualhead output either so
>  only the clone mode works.

Both heads are probably using the same crtc, but xrandr isn't smart
enough to assign a different one.  You can see what crtc is in use by
running xrandr --verbose.  You can assign a different crtc to the
other head like so:
xrandr --output DVI-1 --crtc 1 --mode 1280x1024 --left-of DVI-0

Alex