Bug#595033: xserver-xorg-video-ati: Only one display works at a time with RV620 [FirePro 2260] with two DisplayPort output

[Thomas PIERSON]

Package: xserver-xorg-video-ati
Version: 1:6.13.1-2
Severity: normal

Hi,

I have an issue with 2 monitors connected on two DislpayPort output. The card 
is an ATI "FirePro 2260". And only one display can works at a time.
$ lspci | grep VGA
02:00.0 VGA compatible controller: ATI Technologies Inc RV620 [FirePro 2260]

My issue looks like this archived bug : http://bugs.debian.org/cgi-
bin/bugreport.cgi?bug=569970
> The symptoms are that only one display can be driven at a time.
It also talk about two DisplayPort connections.

So, the 2 monitor are connected and activated in clone mode :

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
DisplayPort-0 connected 1280x1024+0+0 (normal left inverted right x axis y 
axis) 408mm x 255mm
   1680x1050      60.0 +
   1600x1200      60.0  
   1400x1050      60.0  
   1280x1024      75.0     60.0* 
   1440x900       59.9  
   1280x960       60.0  
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
   640x400        70.0  
DisplayPort-1 connected 1280x1024+0+0 (normal left inverted right x axis y 
axis) 380mm x 305mm
   1280x1024      60.0*+   75.0  
   1152x864       75.0  
   1024x768       75.1     60.0  
   800x600        75.0     60.3  
   640x480        75.0     60.0  
   720x400        70.1

But only one display works. 
After that if I run for example :
xrandr --output DisplayPort-0 --left-of DisplayPort-1
I have a black screen on the 2 monitors and I can't access to a terminal.

I noticed something else : When I turn off and on again the second monitor 
(manually) an kernel error occurred :
[18515.140220] [drm:radeon_process_aux_ch] *ERROR* Buffer to small for return 
answer 1 6
During some seconds, the main monitor get stranges color and lights intensity! 

It seem to be the same problem that the bug #569970 but I am not sure.
Someone have an idea to solve this? 
Tell me if you need other logs or informations.

Regards,
Thomas PIERSON

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