arch / xrandr / thunderbolt DP2 screen max resolution 1024x768

Question

just installed recently an Arch-Linux with bspwm on my laptop :

• Dell XPS 9560

  And got my 3 screens working :

  1. Laptop eDP1 screen res. 1920x1080
  2. Acer HDMI1 screen res. 1920x1080
  3. Samsung DP2 screen res. 1024x768

Problem occur with the Samsung screen, xrandr return very limited resolutions choices; the monitor normally works in HD resolution (1920x1080 as well).

Here is the return of my xrandr :

[nox@nox:http/sandra]$ xrandr
(04-11 11:45)
Screen 0: minimum 8 x 8, current 4864 x 1080, maximum 32767 x 32767
eDP1 connected primary 1920x1080+2944+0 (normal left inverted right x axis y axis) 350mm x 190mm
   1920x1080     59.93*+
   1400x1050     59.98  
   1600x900      60.00  
   1280x1024     60.02  
   1280x960      60.00  
   1368x768      60.00  
   1280x720      60.00  
   1024x768      60.00  
   1024x576      60.00  
   960x540       60.00  
   800x600       60.32    56.25  
   864x486       60.00  
   640x480       59.94  
   720x405       60.00  
   640x360       60.00  
DP1 disconnected (normal left inverted right x axis y axis)
DP2 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768      60.00* 
   800x600       60.32    56.25  
   848x480       60.00  
   640x480       59.94  
HDMI1 connected 1920x1080+1024+0 (normal left inverted right x axis y axis) 510mm x 290mm
   1920x1080     60.00*+
   1280x1024     60.02  
   1440x900      59.90  
   1280x800      59.91  
   1152x864      75.00  
   1024x768      70.07    60.00  
   800x600       60.32    56.25  
   640x480       66.67    59.94  
   720x400       70.08  
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

To configure my two Acer & Samsung screens, i'm using commands :

xrandr --output HDMI1 --mode 1920x1080 --left-of eDP1
xrandr --output DP2 --mode 1024x768 --left-of HDMI1

For DP2, if I try to force use 1920x1080 resolution it returns error :

xrandr: cannot find mode 1920x1080

Answer 1

Had similar issue, first I ran:

xrandr --auto

and the correct resolution has appeared. Otherwise read the comment under the original question.