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Hi I have a problem I haven't been able to find any solution for.
The issue is that one of my connected 4K screens randomly goes blank 4-5 times per hour, each occurrence lasting between 1 and 10 seconds.
My setup is a Dell XPS 15 7590, using NVidia GTX 1650 graphics only (running Xorg on the nvidia driver with DRM kernel mode settings enabled). I have a primary 32" 4K Voxicon screen connected directly via HDMI and a secondary identical 32" 4K Voxicon screen connected via DisplayPort from a USB-C dock itself connected to the Thunderbolt 3 port on my XPS.
I know, I know... HDMI and USB-C won't be able to give med 4K @ 60 Hz, but until our IT department can supply me with HDMI2 cables and a Thunderbolt 3-dock, 30 Hz is sufficient for me.
The primary screen connected directly via HDMI works flawlessly, but the one connected via DisplayPort/USB-C randomly goes blank between 1 and 10 seconds, about 4-5 times per hour. When it occurs, there is a ~ 25 % chance that it will happen again within 10 seconds.
I have tried searching for this issue and I have found a multitude of similar problems, with the screen going blank on Nvidia, but most of these threads are ~10 years old, for RedHat or Ubunutu and/or concerns the autolock/screensaver, especially in Gnome. And I'm running Plasma... And Arch ;-) ... In 2020....
Anyway. I have tried every trick from these threads, plus every trick I know in the book to solve this without success.
I have poured through journalctl -fex, but it stays empty when this problem happen.
I have browsed through Xorg.log, but it stays totally silent.
I have tried plugging in my headphones in the problematic screen, without success (In one of the threads I could find, a lot of nvidia users reported this as a workaround).
I have tried disabling the screensaver (kscreensaver)
I have tried the nouveau driver
I have tried switching the screens, to rule out a hardware issue with the secondary screen (but it is always the USB-C/DP connection which blacks out, regardless of physical screen connected)
Unfortunately, I'm unable to connect the 2nd screen directly to my laptop as the XPS only have 1 HDMI2 port available for output, and I don't have any other means of converting the Thunderbolt 3 port to either DVI-D, DisplayPort or HDMI2.
At first, I thought it was related to a media player (youtubemusic-nativefier) which requested a powerdevil inhibition 20-30 seconds prior to the screen going blank, seemingly every time. Unfortunately, it might only be a coincidence. For most of the time, nothing happens after an inhibition is requested, regardless of which application requests it. But most importantly, the screen can go blank without any prior inhibition request. I have also tried playing music through elisa instead, with the same frequency of screen black-outs. I have also tried without any music application active, and the screen still goes blank as often as always. At least some of the times, other applications have requested an inhibition prior to the screen going blank (such as in this journal entry)
Sep 11 08:35:06 dellenite org_kde_powerdevil[1739]: powerdevil: Scheduling inhibition from ":1.269" "/opt/yakyak/yakyak" with cookie 8 and reason "Playing audio"
Sep 11 08:35:09 dellenite org_kde_powerdevil[1739]: powerdevil: Releasing inhibition with cookie 8
Sep 11 08:35:09 dellenite org_kde_powerdevil[1739]: powerdevil: It was only scheduled for inhibition but not enforced yet, just discarding it
Sep 11 08:35:11 dellenite org_kde_powerdevil[1739]: powerdevil: Enforcing inhibition from ":1.269" "/opt/yakyak/yakyak" with cookie 8 and reason "Playing audio"
Sep 11 08:35:11 dellenite org_kde_powerdevil[1739]: powerdevil: By the time we wanted to enforce the inhibition it was already gone; discarding itScreen went blank at roughly 08:35:35, and stayed blank until 08:35:40
I have also, tried to prevent inhibition or try to provoke org.kde.powerdevil myself by sending dbus requests for inhibition, but I haven't been able to trigger a black out event. So I guess this is not related.
Any idea on what more I can do to track down the cause of this behavior?
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USB-C docking station is probably causing random interrupt.
Watching from the healthy screen in terminal, if any number jumps up when it happens.
# watch -n 1 cat /proc/interruptsFrom healthy screen open another terminal, if any process consuming high power when it happens.
# powertopThese are only methods for further investigation, not a solution though.
Last edited by solskog (2020-09-19 10:32:22)
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# watch -n 1 cat /proc/interrupts...
# powertop
I tried to watch both of these outputs and sat there waiting for a while until the screen went blank.
Aaaand... Nothing. :-(
No discernible change in anything.
However, I was able to find multiple users with the same Dell dock, having the exact same issue. Or at least I think it is the same dock. Actually, it seems every single Dell dock experiences this problem in one way or another.
lsusb reports these connected Dell devices
$ lsusb | rg Dell
Bus 004 Device 002: ID 0bda:0487 Realtek Semiconductor Corp. Dell dock
Bus 001 Device 008: ID 413c:b06e Dell Computer Corp. Dell dock
Bus 001 Device 012: ID 413c:b06f Dell Computer Corp. Dell dock
Bus 001 Device 004: ID 0bda:5487 Realtek Semiconductor Corp. Dell dockLooking up the model number, I can confirm it is the Dell WD19 dock. Very similar to these arch users who have the exact same problem with WD19TB (the thunderbolt version of the "same" dock).
I've tried to disable the pulseaudio module-suspend-on-idle as suggested in the Arch wiki for the Dell D6000 dock. I can confirm the module is not loaded with
pactl list modulesbut the problem persists.
I found multiple users on the dell forums nagging about this issue, and all with the same response "we don't support Linux" (even though some of the docks actually lists Linux as a supported system). However one thread was particularly interesting, as multiple users was able to solve the issue by lowering the refresh rate of their connected moniter to 30 Hz. However, I have already lowered my refresh rate to 30 Hz in order to support 4K output. Just in case, I just lowered it even further, down to 25 Hz. The lowest possible refresh rate the plasma systemsettings5 display section detects as a supported refresh rate.
I have also seen one user reporting that connecting a screen via HDMI to the dock fixed the problem. I will certainly try that next week as well. He/she only had the issue when connected via DisplayPort. Another user claimed the issue was solved by installing the "DisplayLink USB Software for Ubuntu", but that was for the Dell D6000 which actually used DisplayLink. The WD19 (and WD19TB) doesn't use DisplayLink, so this will certainly not solve my issue.
For now, I have lowered my refresh rate even further. Down to 25 Hz. I will report back in a few work-days if this solves the issue. Apart from that, I will nag my local "friendly neighborhood IT guy™" (a.k.a. our sysadmin). He's planning to try to update the firmware for the dock. And I guess we can also try to switch to HDMI, or just throw the dock away and try another brand.
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Well, I can rule out that a firmware update solves the issue. The only change was that the WD19 dock just won't play audio any longer.
However, lowering the refresh rate to 25 Hz seems to have "solved" my issue. I'll give it a few more days, and then I'll update the title as [solved], as well as let the other active threads know about this possible workaround.
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With a monitor's refresh rate as low as 25Hz, it could causing your eyes to strain more than necessary in the long run. I am not a expert but only a hint.
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