Bug 498572

Summary:	Unable to get refresh rate higher than 120Hz on Xiaomi Monitor
Product:	[Plasma] KScreen	Reporter:	Luis Mayo <luigidev2>
Component:	common	Assignee:	kscreen-bugs-null <kscreen-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	nate, xaver.hugl
Priority:	NOR
Version First Reported In:	6.2.5
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Luis Mayo 2025-01-12 20:18:29 UTC

SUMMARY
Trying to set my Xiaomi P27FBB-RGGL monitor to any frequency higher than 120HZ doesn't work. Plasma enters a weird state where the screens are constantly flapping between On and Off, the "device connected/disconnected" jingles also start playing.
The only solution at this point is plug the HDMI cable (auto-revert doesn't work somehow?)

STEPS TO REPRODUCE
1. Plug a Xiaomi P27FBB-RGGL monitor via HDMI
2. Change it's frequency to 144 or 165 using System Settings

OBSERVED RESULT
As described, Plasma enters a connect/disconnect loop

EXPECTED RESULT
1. It works properly
2. If it doesn't work properly at least it reverts back to previous frequency automatically, stopping the loop
3. (this is more of a feature request). If it doesn't revert automatically, System settings should ideally have a "forget all displays) button so I don't have to manually remove settings files and restart

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 6.2.5
KDE Frameworks Version: 6.9.0
Qt Version: 6.8.1

ADDITIONAL INFORMATION
I know this is a hard issue for you guys to debug so I hope i can help you with anything you guys need.
I'm running Nobara Linux 41 (based of Fedora KDE 41) with Nvidia GPU (I've tried both with Optimus enabled and disabled through UEFI) on a Laptop

Comment 1 Nate Graham 2025-01-13 19:39:41 UTC

Does this happen on X11, or Wayland, or both?

Comment 2 Luis Mayo 2025-01-13 19:56:28 UTC

Problem was noticed on Wayland. My distro doesn't really offer X11 support by default. But I was able to install verison 6.2.4 of plasma with X11 support and after checking the error is still present there.

Comment 3 Zamundaaa 2025-10-14 16:04:38 UTC

> auto-revert doesn't work somehow?
Hmm, I'm not surprised. auto revert is done by system settings keeping a copy of the old configuration - but if the display in question is removed, the old configuration is no longer valid.

If the display is outright disconnecting, that can only mean that the connection isn't good enough (in which case the driver should filter out the refresh rate from the beginning), or that the display is broken in some way (in which case potentially the driver needs a quirk for it).
Please test with a different cable, and if that too doesn't work, report this at https://forums.developer.nvidia.com/c/gpu-graphics/linux

Comment 4 Luis Mayo 2025-10-19 09:43:23 UTC

Hi!

Sorry I didn't update in long. I was busy with studies.

As you've said, the problem was indeed Nvidia Drivers. For more information it seemed to be a problem with bit color settings (10-bits vs 8-bits). Nvidia has already fixed this in its production branch of the driver.

Sorry for the inconveniences.