Bug 509950

Summary:	Wayland - black screen on LG TV after recent firmware update
Product:	[Plasma] kwin	Reporter:	finalglyph
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	akselmo, kdedev, nate, xaver.hugl
Priority:	NOR
Version First Reported In:	6.4.5
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	the requested logs

Description finalglyph 2025-09-25 20:15:37 UTC

I'm running Arch Linux and KDE Plasma 6.4.5.

I have an LG TV (an OLED B4 model) as a second display. I've been using it at 4K resolution, 120 Hz on Plasma Wayland.

A couple of days ago, I updated the TV's firmware to version 23.23.30. (LG's description of this update is just "fixing minor bugs in software".)

Since then, on Plasma Wayland I get a black screen (display is still detected) regardless of resolution, refresh rate, autosync enabled or not, HDR enabled or not.

On Plasma X11 I get image only if refresh rate is at most 60 Hz. 1080p at 120 Hz still results in black screen. But I didn't try Plasma X11 before the firmware update, so I don't know if this behavior is new.

So basically this "minor" firmware update forced me to downgrade Wayland -> X11, 120 Hz -> 60 Hz and HDR -> SDR.

It's possible LG messed up, but if not, display support in Plasma Wayland shouldn't break this easily.

How can I help you investigate this?

Comment 1 Akseli Lahtinen 2025-09-26 08:39:57 UTC

Can you share more information of your system? (Kernel version, CPU, GPU.. You can copy it from "About this system" in settings)

Does it work in other displays? 

Do you use HDMI or DP or other connection?

Comment 2 finalglyph 2025-09-26 13:37:53 UTC

Thanks for the quick reply.

I didn't find that "about system" tab in settings. (I probably don't have it because I didn't install some optional component of Plasma.)

CPU: AMD Ryzen 5 5600X
GPU: nVidia GeForce RTX 3060 Ti (with proprietary drivers: nvidia 580.82.09-5, linux-firmware-nvidia 20250917-1 <- those are the Arch Linux package names and versions)
kernel version: 6.16.8

Yes, my primary display is a monitor connected via DP (2560 x 1080 @ 144 Hz) and it works well both on Wayland and X11 sessions.

The secondary display (the LG TV) is connected via HDMI.

Both displays are plugged into the nVidia GPU and are arranged side-by-side in the "Display Configuration" settings tab. (When the LG display is black, I can still move the mouse cursor out of the main monitor, but it doesn't appear on the LG display.)

Comment 3 Zamundaaa 2025-10-13 13:44:01 UTC

Please run drm_info while the TV is connected and not receiving a signal, and attach the output of that here

Comment 4 finalglyph 2025-10-13 19:03:57 UTC

Created attachment 185742 [details]
the requested logs

I restarted the computer, selected Plasma Wayland session in the display manager, logged in, and now the LG TV is working properly (4K, 120 Hz) again. I haven't updated any software on the computer or on the TV since I reported the misbehavior.

Comment 5 Zamundaaa 2025-10-14 15:29:12 UTC

To clarify, is the drm_info output now from it working or not working?

If it now works, just close the bug report as "resolved worksforme". If it happens again, just reopen it again.

Comment 6 finalglyph 2025-10-14 17:42:49 UTC

The attached drm_info output is from it working. Sorry for not being clear.

Comment 7 finalglyph 2025-10-14 17:45:54 UTC

Thanks for the help.