Typically, I connect my laptop to a 4k monitor via HDMI. A few months ago, I connected my laptop to a TV via HDMI. After disconnecting it, I can no longer use 4k on the monitor. I may have put the computer to sleep before disconnecting the TV, but I can't be sure. I've searched around the Internet, including Stack Exchange, but haven't found a solution.
When I connect the monitor, I have the option to use 4k, but if I select it, no signal is sent to the monitor. It seems like X really sees the new resolution; I can move my mouse way off in the direction of the monitor, it takes time to move it back. So X sees some desktop space over there.
The laptop is a Dell Precision 5530, with an NVidia Quadro P1000. I'm running Kubuntu 19.10 and the NVidia 440.100 driver. The monitor is an LG 27UD69P. The TV is a Samsung smart TV, but I don't have the model information handy.
Here is my xrandr output. eDP-1-1 is the laptop's built-in display. DP-1-3 is the HDMI connection.
$ xrandr
Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 32767 x 32767
eDP-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
3840x2160 60.00 + 59.98 59.97
3200x1800 59.96 59.94
2880x1620 59.96 59.97
2560x1600 59.99 59.97
2560x1440 59.99 59.99 59.96 59.95
2048x1536 60.00
1920x1440 60.00
1856x1392 60.01
1792x1344 60.01
2048x1152 59.99 59.98 59.90 59.91
1920x1200 59.88 59.95
1920x1080 60.01* 59.97 59.96 59.93
1600x1200 60.00
1680x1050 59.95 59.88
1600x1024 60.17
1400x1050 59.98
1600x900 59.99 59.94 59.95 59.82
1280x1024 60.02
1440x900 59.89
1400x900 59.96 59.88
1280x960 60.00
1440x810 60.00 59.97
1368x768 59.88 59.85
1360x768 59.80 59.96
1280x800 59.99 59.97 59.81 59.91
1152x864 60.00
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
DP-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-3 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 600mm x 340mm
3840x2160 30.00 + 25.00 24.00 29.97 23.98
2560x1440 59.95
1920x1080 60.00* 59.94 30.00 29.97
1920x1080i 60.00 59.94
1600x900 60.00
1280x1024 60.02
1280x800 59.91
1152x864 59.97
1280x720 60.00 59.94
1024x768 60.00
800x600 60.32
720x480 60.00 59.94
640x480 60.00 59.94
