Black screen after monitor power-off on lock screen (KDE Plasma 6, Wayland, NVIDIA, DisplayPort)

Issues & Assistance
1

Hello everyone,

I have been using CachyOS for a while now on my desktop PC, mainly for gaming and general daily use, as part of my transition away from Windows. I recently also installed CachyOS on a Microsoft Surface Book 2 (with a different kernel there) as well, but the issue described below only affects my desktop system. :rofl:

Unfortunately, I am still running into problems related to power management and display handling on my desktop. There are two related issues (monitor power-off on lock screen and system sleep), but to keep things structured, I would like to focus on the monitor power-off behavior first.

The issue seems very similar to this thread: Long black screen after login and KDE session crash after some minutes and maybe this thread: Can't suspend system with NVIDIA .

I have been investigating this for quite some time, including extensive log analysis and testing different configuration changes, but so far without a reliable solution.

**Problem description:
**
When the screen is locked and the monitor is powered off automatically after the configured timeout, the expected behavior would be that the lock screen reappears when user input occurs (for example, moving the mouse or pressing a key).

What actually happens instead:

  • The monitor wakes up (backlight turns on).
  • Immediately after that, it turns off again because it reports no signal.
  • The system itself is still running and responsive.

A workaround that consistently restores the session is switching to a TTY via Ctrl + Alt + F3 and then switching back to the graphical session via Ctrl + Alt + F2.

After doing this, the desktop session continues normally. However, this is obviously not a real solution, and I would like to fix the underlying problem.

My System:
  • Distribution: CachyOS (fully up to date at the time of testing)
  • Desktop environment: KDE Plasma 6
  • Session type: Wayland (kwin_wayland)
  • GPU: NVIDIA GeForce RTX 4080 SUPER
  • Driver: NVIDIA proprietary driver 580.119.02 (open kernel module, DRM enabled)
  • Kernel: CachyOS default desktop kernel
  • Display connection: DisplayPort
  • Monitor: Samsung Odyssey OLED G93SC
  • Resolution: 5120Ă—1440
  • Refresh rate: up to 240 Hz
  • HDR enabled
  • Adaptive Sync tested both enabled and disabled
What I have already tried:
  1. Tested different monitor settings:
    1. Adaptive Sync enabled and disabled
    2. Various monitor-side power-saving related options disabled
  2. Tested different display modes and refresh rates via kscreen-doctor.
  3. Ensured that nvidia-drm.modeset=1 is enabled.
  4. Verified that the monitor is correctly detected via DRM:
    1. /sys/class/drm/card*-DP-*/status shows connected
    2. EDID is present and readable
  5. Checked DDC/CI access via ddcutil (monitor detected correctly).
  6. Temporarily adjusted permissions and group membership for i2c to rule out DDC permission issues (no change in behavior).
  7. Reviewed and tested NVIDIA suspend and resume handling, including:
    1. nvidia-suspend.service
    2. nvidia-resume.service
    3. nvidia-hibernate.service
  8. Tested NVIDIA’s video memory preservation approach as described here:
    NVIDIA/Tips and tricks - ArchWiki
  9. Tested setting SYSTEMD_SLEEP_FREEZE_USER_SESSION=true (as suggested in a related discussion), but this did not change the behavior in my case.

I have uploaded the log files generated with the help of ChatGPT kwin-debug-20251226-102849.tar.gz here:

and the output from sudo cachyos-bugreport.sh is here:

If additional logs or debug flags are required, I am happy to provide them.

The issue appears to be related to KDE Plasma 6 + Wayland + NVIDIA + DisplayPort, specifically when the monitor powers off while the session is locked. From the logs, it looks like KWin temporarily loses all outputs (“no outputs – creating placeholder screen”), and the session does not properly recover the display without a TTY switch.

Any hints, similar experiences, or pointers to known issues would be greatly appreciated.

Thanks in advance for your time and help.

Best regards,
Sebastian

2

I’m having the exact same problem. Even if I make sure I switch back to internal monitor only before disconnecting from an external display sometimes when I open the laptop again it’s black.

I try logging in blind, then playing with the select display function key but that doesn’t work. I try opening a terminal with the shortcut key, typing reboot and pressing enter. That doesn’t work either.

Ctrl + Alt + F3 and then switching back to the graphical session via Ctrl + Alt + F2 didn’t work. I tried both before logging in and after logging in blind.

This is starting to annoy me.

I have a Dell latitude 7480 with Intel i7) running CachyOS KDE plasma on Wayland.

3

Same issue here with an AMD iGPU and HDMI. I tested KDE Plasma under Fedora as well and it shows almost the same behavior. Cachy with Gnome works fine.

When I start without my monitor turned on, I end up in a black screen, where I can see and move a mouse cursor.

I suspected some power/hibernation settings, but they had no impact.

This is really a deal breaker for me.

4

I had the same problem with my intel+nvidia hybrid laptop, but in my case your temporary solution is “kinda work”. Sometimes I also have to change display configuration to “mirror screens” then my monitor is back to normal. I really like CachyOS KDE but this is very annoying.

5

Does anyone have a solution? This problem is still present. I have a RX 9070XT. When the monitor wakes up from sleep, the dekstop is black sometimes. I have to logout and login to fix it.