Ubuntu – Screen freezes when attempting changes in xrandr

17.10display-resolutionmultiple-monitorsradeonxrandr

I am trying to use my external LCD display (BenQ V2200 Eco Specs) with my laptop (hp from about HP Compaq 6910 p with Lubuntu 17.10 with the latest updates).

When plugging the display while using monitor settings the screen stays black, no signal. When plugging it before booting, it runs but with the wrong resolution.

I believe xrandr is set in order to extend the desktop over both the laptop screen and the external LCD display, but the actual resolution on the LCD is 3200×1080 instead of 1920×1080, so the desktop is cropped on the right. The problem is that if I attempt any changes in the settings in xrandr or arandr, the screens freeze and I need to do a hard reboot. This also happens if I make changes without the external display being plugged in.

$ lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV516/M64-S [Mobility Radeon X2300]

$ lspci -nnk | grep -i vga -A3 | grep 'in use'
    Kernel driver in use: radeon

This is the output of xrandr (if I plug the display in the running computer; if I plug it before booting, current changes to 3200×1080):

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 8192 x 8192
VGA-0 connected primary (normal left inverted right x axis y axis)
   1920x1080     60.00 +
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1280x800      59.81  
   1152x864      75.00  
   1280x720      60.00  
   1024x768      75.03    60.00  
   1024x576      59.97  
   832x624       74.55  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
   720x400       70.08  
LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 304mm x 190mm
   1280x800      60.00*+
   1280x720      59.97  
   1152x768      59.95  
   1024x768      59.95  
   800x600       59.96  
   848x480       59.94  
   720x480       59.94  
   640x480       59.94  
S-video disconnected (normal left inverted right x axis y axis)
DVI-0 disconnected (normal left inverted right x axis y axis)

Best Answer

As you said when you plug the monitor before booting it gives a bad resolution, I believe adding a particular resolution in .profile would solve this issue.

Open the terminal and run the following command.

xrandr

xrandr output

Note the display device name from the output.In my case its eDP-1.

next run the following command 

cvt 1920 1080

command output in terminal

Copy the whole Modeline from the output.

In my case it is as follows 

"1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync.

And run the following command:

sudo xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync

NOTE the command sections after --newmode are copied from the output I got in the previous step.

Now add the newly created mode for your display device.

sudo xrandr --addmode eDP-1 "1920x1080_60.00"

Finally Apply the new resolution in the Display settings. Select the "1920x1080" resolution as your preferred resolution.

IMPORTANT: To make Ubuntu remember the new created screen resolution at next start, you have to edit your .profile. Use any text editor, for example:

vim ~/.profile

add the last 2 commands to the end

profile in vim

Save and reboot. Hopefully the system will detect 1920x1080 resolution in both your displays.

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