Ubuntu 20.04 GTX970M Display via Display Port detected but mainly black

Graphics / Linux Linux
1

Hi lads, since the last nvidia update my second external display [via Display Port] connected to my laptop stopped working most of the time. Sometimes after reconnecting it will pop up for a while and then turns black again. The first external display via HDMI works fine. I crosschecked everything [display/cables] but i can’t figure it out.
I tried everything i could find in several forums, here are some outputs of my terminal:

xrandr:

Screen 0: minimum 8 x 8, current 5760 x 1080, maximum 16384 x 16384
VGA-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 521mm x 293mm
1920x1080 60.00*+ 59.94 50.00
1680x1050 59.95
1600x900 60.00
1440x900 59.89
1280x1024 60.02
1280x800 59.81
1280x720 60.00 59.94 50.00
1024x768 70.07 60.00
800x600 72.19 60.32 56.25
720x576 50.00
720x480 59.94
640x480 72.81 59.94
DP-0 connected primary 1920x1080+3840+0 (normal left inverted right x axis y axis) 344mm x 194mm
1920x1080 60.02*+ 47.99
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 521mm x 293mm
1920x1080 60.00*+ 59.94 50.00
1680x1050 59.95
1600x900 60.00
1440x900 59.89
1280x1024 60.02
1280x800 59.81
1280x720 60.00 59.94 50.00
1024x768 70.07 60.00
800x600 72.19 60.32 56.25
720x576 50.00
720x480 59.94
640x480 72.81 59.94
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)

prime-select nvidia:

Info: the nvidia profile is already set

rm /etc/modprobe.d/blacklist-nvidia.conf /lib/modprobe.d/blacklist-nvidia.conf:

rm: cannot remove ‘/etc/modprobe.d/blacklist-nvidia.conf’ : No such file or directory
rm: cannot remove ‘/lib/modprobe.d/blacklist-nvidia.conf’ : No such file or directory

nvidia-smi:

Thu Feb 18 09:37:47 2021
±----------------------------------------------------------------------------+
| NVIDIA-SMI 460.32.03 Driver Version: 460.32.03 CUDA Version: 11.2 |
|-------------------------------±---------------------±---------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
| | | MIG M. |
|===============================+======================+======================|
| 0 GeForce GTX 970M Off | 00000000:01:00.0 On | N/A |
| N/A 56C P0 20W / N/A | 442MiB / 6082MiB | 0% Default |
| | | N/A |
±------------------------------±---------------------±---------------------+

±----------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=============================================================================|
| 0 N/A N/A 1178 G /usr/lib/xorg/Xorg 80MiB |
| 0 N/A N/A 1880 G /usr/lib/xorg/Xorg 183MiB |
| 0 N/A N/A 2020 G /usr/bin/gnome-shell 165MiB |
±----------------------------------------------------------------------------+

lsb_release -a:

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.2 LTS
Release: 20.04
Codename: focal

And my log file:

nvidia-bug-report.log.compressed (569.1 KB)

Thanks a lot for help, this is driving me nuts.

2

Actually, this rather looks like the hdmi connected samsung display has a problem, the link speed always toggles between 165/600MHz. The driver is always resetting modes on occurance. Might be a nearly broken cable. Maybe at some time the displayport gets confused or thrown out. Does the DP connected LG stay on if you remove the samsung?

3

Hi pal, thanks for quick reply and your help.
If i disconnect the HDMI display, the DP display won’t pop up again. The displays are the same, both Samsung CF24F390. i changed the HDMI cable now as well.
nvidia-bug-report.log.compressed (762.3 KB)

4

Ok, I got confused by your internal display and the fact that the monitor on DP actually uses an hdmi converter dongle. So it’s not the same monitor toggling speeds but two monitors at different speeds. Telling which is which is impossible, I guess the one running at 165MHz is using the converter which would point to it being broken. A very simple passive adapter should bring you to 300MHz TMDS, AFAIK.

5

Thanks pal. So to understand it correct. I’m using a brand new DP to HDMI cable on the DP port. That’s broken?
I have 3 “Chinese” [ordered via ebay from China] HDMI to DP adapters/cables, which i was using, when the issue occurred first. Now i especially ordered a"brandname" cable, which is now connected…and that’s broken then.
Sorry for my follow-up questions.
I really appreciate your time and effort spent.

6

You’re a star my friend. Thanks for pointing the HDMI cable issue out to me.
Original Samsung HDMI cable + “chinese” HDMI to DP converter and my screen pops up again.
I tried so many combinations before, but now it looks like we found one, that’s working.
Thanks a lot pal, i wish you a pleasant week.