(In reply to Elite from comment #0)
> SUMMARY
> When the display is set to its default resolution and refresh rate it cause
> white lines similar to old static. this also happens in the SDDM and then
> things are set to default breeze. Changing DP results in the same problem.
> This does not happen when on the same system from the sddm logging into
> another DE. Or even if they are all fully removed.  I have also tried
> another monitor of the same make and model and same gpu make and model. All
> give the same result. 
> I did notice that it happens in the sddm if I log out. 
> It manly happens when there any  movement on screen moving a mouse moving a
> blinking terminal courser. When dragging a window back an forth it doesn't
> seem to happen tell the window stops moving. It used to be fixed for a while
> by setting any other refresh rate not saving and going back to 144hz. I cant
> capture it on video either. its almost like screen tearing or vsync is
> having some issue. I have adaptive sync fully disabled on the monitor as
> well. 
> 
> If the monitor is set to DP 1.2, it no longer happens but the display can no
> longer hit its default refresh rate so everything  looks choppy. 
> I don't remember this happening in 6.3.2.
> 
> STEPS TO REPRODUCE
> 1. Make sure the monitor supports DP 1.4 set refresh rate to 144hz or
> higher. 
> 2. open a video played from a local file or a long config in kate 
> 3. play or scroll the text file.
> 
> OBSERVED RESULT
> White Lines randomly over the display.
> 
> EXPECTED RESULT
> no lines 
> 
> SOFTWARE/OS VERSIONS
> Operating System: NixOS 25.11
> KDE Plasma Version: 6.3.5
> KDE Frameworks Version: 6.14.0
> Qt Version: 6.9.0
> Kernel Version: 6.14.7-cachyos (64-bit)
> Graphics Platform: Wayland
> Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
> Memory: 31.2 GiB of RAM
> Graphics Processor: AMD Radeon RX 7900 GRE
> 
> ADDITIONAL INFORMATION
> 
> System:
>   Kernel: 6.14.7-cachyos arch: x86_64 bits: 64 compiler: gcc v: 14.2.1
>     clocksource: tsc avail: hpet,acpi_pm
>     parameters:
> initrd=\EFI\nixos\1y87izfnn4ayic3n47x2y45s5fqajx0w-initrd-linux-6.14.7-
> initrd.efi
>    
> init=/nix/store/hnvax2y675x99bfihsmc9vmasgg868l3-nixos-system-nixos-25.11.
> 20250520.2795c50/init
>     quiet splash rd.systemd.show_status=false rd.udev.log_level=3
>     udev.log_priority=3 loglevel=3 plymouth.force-splash boot.shell_on_fail
>     psi=1 splash loglevel=0
>   Desktop: KDE Plasma v: 6.3.5 tk: Qt v: N/A info: frameworks v: 6.14.0
>     wm: kwin_wayland vt: 4 dm: SDDM Distro: NixOS 25.11 (Xantusia)
> Machine:
>   Type: Desktop Mobo: ASUSTeK model: PRIME X570-PRO v: Rev X.0x
>     serial: <superuser required> part-nu: SKU uuid: <superuser required>
>     UEFI: American Megatrends v: 5031 date: 01/13/2025
> CPU:
>   Info: model: AMD Ryzen 7 3700X bits: 64 type: MT MCP arch: Zen 2 gen: 2
>     level: v3 note: check built: 2020-22 process: TSMC n7 (7nm)
>     family: 0x17 (23) model-id: 0x71 (113) stepping: 0 microcode: 0x8701035
>   Topology: cpus: 1x dies: 1 clusters: 1 cores: 8 threads: 16 tpc: 2
>     smt: enabled cache: L1: 512 KiB desc: d-8x32 KiB; i-8x32 KiB L2: 4 MiB
>     desc: 8x512 KiB L3: 32 MiB desc: 2x16 MiB
>   Speed (MHz): avg: 4261 min/max: 560/4427 boost: enabled scaling:
>     driver: amd-pstate-epp governor: performance cores: 1: 4261 2: 4261 3:
> 4261
>     4: 4261 5: 4261 6: 4261 7: 4261 8: 4261 9: 4261 10: 4261 11: 4261 12:
> 4261
>     13: 4261 14: 4261 15: 4261 16: 4261 bogomips: 115197
>   Flags: avx avx2 ht lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm
>   Vulnerabilities: <filter>
> Graphics:
>   Device-1: Advanced Micro Devices [AMD/ATI] Navi 31 [Radeon RX 7900 XT/7900
>     XTX/7900 GRE/7900M] vendor: Sapphire driver: amdgpu v: kernel arch:
> RDNA-3
>     code: Navi-3x process: TSMC n5 (5nm) built: 2022+ pcie: gen: 4
>     speed: 16 GT/s lanes: 16 ports: active: DP-1 empty: DP-2, HDMI-A-1,
>     HDMI-A-2, Writeback-1 bus-ID: 0d:00.0 chip-ID: 1002:744c class-ID: 0300
>   Display: wayland server: X.org v: 1.21.1.16 with: Xwayland v: 24.1.6
>     compositor: kwin_wayland driver: gpu: amdgpu display-ID: 0
>   Monitor-1: DP-1 model: LG (GoldStar) ULTRAGEAR serial: <filter>
>     built: 2020 res: 3440x1440 dpi: 109 gamma: 1.2 size: 800x335mm
> (31.5x13.19")
>     diag: 867mm (34.1") modes: max: 3440x1440 min: 640x480
>   API: Vulkan Message: No Vulkan data available.
>   API: EGL Message: EGL data requires eglinfo. Check --recommends.
>   Info: Tools: api: clinfo,vulkaninfo de: kscreen-console,kscreen-doctor
>     gpu: lact x11: xprop,xrandr
> Audio:
>   Device-1: Advanced Micro Devices [AMD/ATI] Navi 31 HDMI/DP Audio
>     driver: snd_hda_intel v: kernel pcie: gen: 4 speed: 16 GT/s lanes: 16
>     bus-ID: 0d:00.1 chip-ID: 1002:ab30 class-ID: 0403
>   Device-2: Advanced Micro Devices [AMD] Starship/Matisse HD Audio
>     vendor: ASUSTeK driver: snd_hda_intel v: kernel pcie: gen: 4 speed: 16
> GT/s
>     lanes: 16 bus-ID: 0f:00.4 chip-ID: 1022:1487 class-ID: 0403
>   Device-3: BurrBrown from Texas Instruments USB AUDIO CODEC
>     driver: hid-generic,snd-usb-audio,usbhid type: USB rev: 2.0 speed: 12
> Mb/s
>     lanes: 1 mode: 1.1 bus-ID: 1-1:2 chip-ID: 08bb:29c0 class-ID: 0300
>   API: ALSA v: k6.14.7-cachyos status: kernel-api
>     tools: alsactl,alsamixer,amixer
>   Server-1: PipeWire v: 1.4.2 status: active with: 1: pipewire-pulse
>     status: active 2: wireplumber status: active 3: pipewire-alsa type:
> plugin
>     tools: pw-cat,pw-cli,wpctl
>   Server-2: PulseAudio v: 17.0 status: off (using pipewire-pulse)
>     tools: pacat,pactl
> Network:
>   Device-1: Intel Wireless 7260 driver: iwlwifi v: kernel pcie: gen: 1
>     speed: 2.5 GT/s lanes: 1 bus-ID: 06:00.0 chip-ID: 8086:08b1 class-ID:
> 0280
>   IF: wlp6s0 state: down mac: <filter>
>   Device-2: Intel I211 Gigabit Network vendor: ASUSTeK driver: igb v: kernel
>     pcie: gen: 1 speed: 2.5 GT/s lanes: 1 port: f000 bus-ID: 07:00.0
>     chip-ID: 8086:1539 class-ID: 0200
>   IF: enp7s0 state: up speed: 1000 Mbps duplex: full mac: <filter>
>   IF-ID-1: docker0 state: down mac: <filter>
>   IF-ID-2: virbr0 state: down mac: <filter>
>   Info: services: NetworkManager, smbd, systemd-timesyncd, wpa_supplicant
> Bluetooth:
>   Device-1: N/A driver: btusb v: 0.8 type: USB rev: 2.0 speed: 12 Mb/s
>     lanes: 1 mode: 1.1 bus-ID: 3-6:3 chip-ID: 8087:07dc class-ID: e001
>   Report: hciconfig ID: hci0 rfk-id: 0 state: up address: <filter> bt-v: 4.0
>     lmp-v: 6 sub-v: e00 hci-v: 6 rev: e00 class-ID: 7c0104
>   Info: acl-mtu: 1021:5 sco-mtu: 96:6 link-policy: rswitch hold sniff
>     link-mode: peripheral accept service-classes: rendering, capturing,
> object
>     transfer, audio, telephony
> Sensors:
>   System Temperatures: cpu: 47.0 C mobo: 40.0 C gpu: amdgpu temp: 52.0 C
>     mem: 68.0 C
>   Fan Speeds (rpm): N/A gpu: amdgpu fan: 0
> Info:
>   Memory: total: 32 GiB available: 31.25 GiB used: 7.29 GiB (23.3%)
>   Processes: 439 Power: uptime: 10h 15m states: freeze,mem,disk
>     suspend: deep avail: s2idle wakeups: 0 hibernate: platform avail:
> shutdown,
>     reboot, suspend, test_resume image: 12.48 GiB services:
> org_kde_powerdevil,
>     power-profiles-daemon, upowerd Init: systemd v: 257 default: graphical
>     tool: systemctl
>   Packages: 4006 pm: nix-default pkgs: 2 pm: nix-sys pkgs: 3635 libs: 794
>     pm: nix-usr pkgs: 294 libs: 52 pm: flatpak pkgs: 75 Compilers: clang:
> 19.1.7
>     gcc: 14.2.1 Shell: fish v: 4.0.2 default: Bash v: 5.2.37
>     running-in: .kitty-wrapped inxi: 3.3.38

This also only happens in wayland as i just tested it in x11 an could not replicate it.

I have had this too occasionally, however for me it usually fixes itself when replugging the Displayport cable. 
I've never been able to repro this reliably though.

Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.80
KDE Frameworks Version: 6.15.0
Qt Version: 6.9.0
Kernel Version: 6.14.6-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 3600 6-Core Processor
Memory: 16 GiB of RAM (15.5 GiB usable)
Graphics Processor: AMD Radeon RX 6600

This is almost certainly coming from memory frequency switching in the driver, please report this at https://gitlab.freedesktop.org/drm/amd/-/issues (there's already some similar issues reported)

If you want a workaround, adaptive sync options could make a difference.

I want to report the issue is back it was gone in kde 6.4.3 and came back in 6.4.4 the kernel has not changed from Linux 6.16.0-rc7-cachyos in both versions of kde. It only happens in kde as I have tested it in wayfire and trinity. So wayland and x11 and, a fresh arch kde install as well.

Changing refresh rate stops it tell either the display shuts off or the system is turned on from a power off state. Adaptive sync seems to not change anything no matter which setting it is set to. I only bring this back up because it could cause seizures.

If there are any logs or thing I could get to help in reporting please let me know and I will do it right away.

Operating System: NixOS 25.11
KDE Plasma Version: 6.4.4
KDE Frameworks Version: 6.16.0
Qt Version: 6.9.1
Kernel Version: 6.16.0-rc7-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
Memory: 32 GiB of RAM (31.2 GiB usable)
Graphics Processor: AMD Radeon RX 7900 GRE

> I want to report the issue is back it was gone in kde 6.4.3 and came back in 6.4.4
Changes in kwin can trigger or not trigger it, but it's still a bug in the kernel that we can't fix in KWin.