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I know there are a million questions like this one, but I still feel this has it's own unique set of problems.

The main issue is: I want to run my external monitor in 4K resolution above 50Hz

xrandr clearly shows 3840x2160@50.00 Hz as an option (see output below) and it shows up as an option in every GUI, however - it just doesn't work.

X.org: As soon as I pick it the screen blanks out and reverts back to 4k@30Hz or 1440@60 Hz (whatever I was running before). Wayland: Wayland will claim it's running at 4K, but the DPI is to low. This means I only can see something like 1920x1080 pixels on my monitor and the remaining 3/4 of the desktop is displayed outside my monitor - making it impossible to use. I should be noted I have no interest in running wayland unless it makes my life easier :) I just provided the information here because I found it interesting.

One would think this could be due to a faulty cable, but my two other windows laptops I tried has managed to run 4K@60Hz (or 50Hz) just fine, so the bandwidth from the dock to the monitor seems to be high enough.

The hardware setup is as follows:

  • laptop (with the issue): Thinkpad P43s
  • Running Ubuntu 22.10 with version 525.89.02 of the nvidia drivers
  • a dock: Lenovo ThinkPad USB-C Dock Gen2. Connected to the laptop using Thunderbolt 3
  • a monitor: Dell s3221qs (connected with displayport 1.2)

I've also included the verbose output of me setting the resolution manually from the command line. 4K@30Hz works while 50Hz does not for some reason

If anyone have any good idea for what to try next - I would love to hear them.

Output from xrandr:

myuser@myuser-ThinkPad-P43s:~$ xrandr
Screen 0: minimum 320 x 200, current 4480 x 1440, maximum 16384 x 16384
eDP-1 connected 1920x1080+0+360 (normal left inverted right x axis y axis) 309mm x 173mm
   1920x1080     60.00*+  60.00  
   1680x1050     60.00  
   1400x1050     60.00  
   1600x900      60.00  
   1280x1024     60.00  
   1400x900      60.00  
   1280x960      60.00  
   1440x810      60.00  
   1368x768      60.00  
   1280x800      60.00  
   1280x720      60.00  
   1024x768      60.00  
   960x720       60.00  
   928x696       60.00  
   896x672       60.00  
   1024x576      60.00  
   960x600       60.00  
   960x540       60.00  
   800x600       60.00  
   840x525       60.00  
   864x486       60.00  
   700x525       60.00  
   800x450       60.00  
   640x512       60.00  
   700x450       60.00  
   640x480       60.00  
   720x405       60.00  
   684x384       60.00  
   640x360       60.00  
   512x384       60.00  
   512x288       60.00  
   480x270       60.00  
   400x300       60.00  
   432x243       60.00  
   320x240       60.00  
   360x202       60.00  
   320x180       60.00  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-2-1 disconnected (normal left inverted right x axis y axis)
DP-2-2 disconnected (normal left inverted right x axis y axis)
DP-2-3 connected primary 2560x1440+1920+0 (normal left inverted right x axis y axis) 697mm x 392mm
   3840x2160     50.00    30.00    25.00    24.00    29.97    23.98  
   2560x1440     59.95* 
   1920x1200     59.88  
   1920x1080     60.00    50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.95  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08

Set resolution from command line

myuser@myuser-ThinkPad-P43s:~$ xrandr --output DP-2-3 --mode 3840x2160 --rate 50.00 --verbose
screen 0: 3840x2160 1016x571 mm  96.00dpi
crtc 0:    3840x2160  50.00 +0+0 "DP-2-3"
xrandr: Configure crtc 0 failed
crtc 0: disable
crtc 1: disable
crtc 2: disable
screen 0: revert
crtc 0: revert
crtc 1: revert
crtc 2: revert
myuser@myuser-ThinkPad-P43s:~$ xrandr --output DP-2-3 --mode 3840x2160 --rate 30.00 --verbose
screen 0: 3840x2160 1016x571 mm  96.00dpi
crtc 0:    3840x2160  30.00 +0+0 "DP-2-3"
myuser@myuser-ThinkPad-P43s:~$
Michael Hansen
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  • Have you already tried setting a custom resolution using cvt to give you the proper output to input into xrandr? Possibly for 60Hz instead of 50 considering that it appears you're running on 60Hz (North America?) as it wants to default to 30. – mchid Mar 24 '23 at 21:37
  • So probably cvt 3840 2160 60 – mchid Mar 24 '23 at 21:38
  • @mchid I did previously, and I just tried again. Still same problem where it tries and falls back. Same output from xrandr as in the original post (crtc 0 failed). I'm actually in Europe and I've try everything with both 50 and 60 Hz – Michael Hansen Mar 24 '23 at 21:51
  • You could try cvt -r 3840 2160 60 (reduced blanking mode). Although I have seen lots of reports here which seem to be related to docks - I think Ubuntu works well with direct PC/monitor connections but perhaps these docks require additional driver support and are supported on Windows but not on Linux? As all the dock issues seem to be "it works on Windows but not on Ubuntu". – codlord Mar 25 '23 at 10:13
  • @codlord you might be right. I actually considered buying a Displayport to usb c cable just to remove the dock from the equation. But then again, it doesn't really solve my problem because I need a dock :) anyway. you command didn't work – Michael Hansen Mar 25 '23 at 15:14
  • @codlord I did some more googling and it is definitely a compatibility issue between the dock and ubuntu. Not something which can be solved at the moment, but I will try with an older dock I have somewhere. At least I know I can stop trying to fix it running various commands – Michael Hansen Mar 25 '23 at 15:33

0 Answers0