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#1 2021-05-31 10:33:38

Registered: 2020-12-09
Posts: 2

System crash/black screen when enabling an external monitor


As the title says, I get a black screen and what seems to be a system crash when I try to plug any monitor on the HDMI port of my laptop when it’s turned on. I searched several times on the internet to see if this problem was known, but either I didn’t search with the right keywords, or I’m searching for something that has not been identified at the moment, the fact remains that I didn’t find any relevant solutions or problems.
I, then, did several tests to try to determine in which cases this problem exactly happens and if I could identify the source of the it. The blank black screen, as the system crashes, affects both monitors.

Here’s a short but probably relevant list of information about my laptop and Linux installation:
OS: Arch Linux x86_64
Host: VivoBook 12_ASUS Laptop E203MAS_E203MA 1.0
Kernel: 5.12.7-arch1-1
Resolution: 1366x768
DE: Plasma 5.21.5
WM: KWin
CPU: Intel Pentium Silver N5000 (4) @ 2.700GHz
GPU: Intel UHD Graphics 605

* I don’t have any of these problems on the same machine with Windows 10.
* I encounter them both on and Wayland.
* As I can’t switch to a new tty and can’t control anything, either with KdeConnect or ssh, and as when the screens becomes black, all audio streams (on speaker or jack line out) are stopped, I think we can consider that it’s not only a crash but a crash of almost the whole system.
    * However, when my phone is connected with Bluetooth to my laptop, the system/bluez/KDE-with-bluedevil automatically routes the phone’s audio streams to the laptop’s audio output. This way, I found by accident that when the system crashes, the audio streams from my phone are still read on the laptop audio output used before the crash (e.g. plugging in headphones on the jack port stops the sound of the speakers but doesn’t switch to the headphones, and unplugging it restore the sound on speakers).
Maybe things are directly routed from BT device to the laptop’s BT chip to the laptop’sound chip then to the laptop’speakers/jack line, so nothing pass through the system and thus stops when it crashes…
* Going into the Kde’s display settings (or using another X/RandR configuration tool like LxRandR or aRandR) and disabling the external screen to enable it again is the equivalent of hot-plugging the screen,
* There is no problems when unplugging the monitor: the entire display switches to the laptop builtin monitor and I can continue using it as usual, without rebooting,
* It crashes too when I plug the monitor after the `Starting·Finished Load/Save Screen Backlight Brightness of backlight:intel_backlight` log line during boot is shown, BUT I can un·plug the screen in SDDM as many times I want, and SDDM will just choose the smallest resolution between the monitors and use it to render the display on both monitor (e.g. a 1920×1080 monitor will display at my laptop’s 1366×768 resolution, and a 1280×720 monitor will make my laptop’s render at the monitor’s resolution)
* I thought it was kscreen’s fault and that disabling it would solve things but in fact it didn’t changed a lot of things, and even made some things worse:
    — I still have to plug the monitor before the boot or in SDDM,
    — but when unplugging the external monitor, the screen layout’s auto-config is not made anymore: the display remains the same as with the external monitor plugged in, so windows and cursor still display on this second screen and I can move them… blindly :D
    — If I plug the monitor in SDDM when kscreen is disabled, the external monitor is not automatically enabled.
    — Next, if I enable kscreen again, it enables automatically the second monitor then the system crashes. However, when kscreen is disabled but I plug in the monitor before the boot, both monitor will display the same things (with the resolution of both screens being the one of the smaller screen, as already said in the upper brackets), and enabling kscreen will automatically and properly set the resolution and placement of both screens, according to the previously chosen settings, without any crash.

So the thing is that I just need to plug the screen at boot to not encounter any problems, but it is really not convenient for a laptop, and the problem really seems to be with this activation of a new monitor.

I really don’t know what logs of which programs or tool I can look at to investigate deeper, so I surely need the help from the Arch community to solve this.

Have a nice day,

Last edited by Aznörth (2021-11-11 22:24:01)


#2 2021-11-12 12:54:20

Registered: 2020-12-09
Posts: 2

Re: System crash/black screen when enabling an external monitor

I searched for some logs.
Starting dmesg -w -k -H > output_file to get logs of the activation writes nothing in the file, and journalctl /usr/lib/kf5/kscreen_backend_launcher outputs nothing, as well as journalctl, which output nothing relevant about the «crash» itself. Nevertheless, as the only way to power off my computer is forcing it to turn off with a long press on the power button, I observe in journalctl a Power key pressed line, followed by some logs after the "crash", about modules and services extinction. However, if I just press shortly the Power button, the machine never turns off, even after waiting. So the crash seems to not be total. lines about the activation of HDMI1 seems irrelevant too, as it’s just informative, and nothing is output after that:

[   815.760] (II) intel(0): switch to mode 1280x720@60.0 on HDMI1 using pipe 1, position (0, 0), rotation normal, reflection none

I don’t have any problems when I enable my internal monitor, and the problem is the same with other DE like i3 or LxQt.

Would there be other relevant logs I could search in ?

EDIT: Also, I tried disabling TLP systemd service, as it can sometimes create mayhem, but nothing changed. I enabled it again.

EDIT2: Is there a way in BBCode to use a monospace font like the `` in markdown? It seems that the font=monospace tag doesn’t work on ArchForums, and the code tag creates a block of text separate of the rest of the line.

Last edited by Aznörth (2021-11-14 11:12:26)


#3 2021-11-27 02:37:28

Registered: 2021-11-27
Posts: 1

Re: System crash/black screen when enabling an external monitor

Hi! Happy to finally find a report of an issue I have been looking for an answer without success. It turns out I found this thread when I was looking for another thing, so lol.

I have the same issue as you, we have different laptops but our CPU and GPU are the same, and I'm using Arch with Plasma 5,23, but may have been dragging this situation probably since one or two versions ago. My problem seems to be a little more critical since I can't recover when I unplug the external monitor (In my case a TV) through HDMI, my only solution is forcing a reboot. I have tried executing some reboot, suspend, lock and unlock commands using KDE Connect, unsuccesfully. Could you please share the commands you use to re-enable kscreen (if you use the command line)? to check if it works using KDE Connect.

I will try to check if my scenario is similar to yours in other situations. Until now I could only partially confirm it is a Plasma thing because it didn't happen during a session with a WM (I guess the screen sharing there isn't automatic so I may be wrong).

Have a nice day! smile


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