https://bugs.kde.org/show_bug.cgi?id=494128
--- Comment #8 from [email protected] --- --- This is a regression comment on Bug 494128. --- Summary Black level is elevated (grey/grainy appearance) on OLED display when HDR is enabled in KWin 6.6.x over HDMI at 120Hz. Regression from a previously working state. Environment - OS: Bazzite 43.20260313 (Fedora 43) - KDE Plasma: 6.6.2 - KWin: 6.6.2-2.fc43 (also confirmed on 6.6.2-1 and 6.6.1-1) - Mesa: 26.0.2 (also confirmed on 26.0.1) - Kernel: 6.17.7-ba28.fc43.x86_64 - GPU: AMD Radeon RX 7900 XTX (Navi 31, amdgpu, DMUB fw 0x07002F00) Display - Monitor: ASUS ROG Swift PG27AQDM (OLED, firmware MCM110) - Connection: HDMI (connector HDMI-A-2) - Resolution/Refresh: 2560x1440 @ 120Hz - VRR: Automatic Symptom When HDR is enabled in Display Settings, black areas on the OLED panel appear as a grey/grainy haze instead of pure black. Critically, blacks are accurate for approximately 1-2 seconds immediately after enabling HDR, then the grey haze appears as KWin's colour pipeline fully initialises. This timing strongly suggests something in the pipeline initialisation is lifting the black floor. Night Light also becomes excessively orange when the issue is active, indicating the full colour pipeline is affected, not just black level. Conditions ┌─────────────────────────────────┬────────────────────────┐ │ Scenario │ Result │ ├─────────────────────────────────┼────────────────────────┤ │ HDR on, HDMI 120Hz │ Grey blacks — affected │ ├─────────────────────────────────┼────────────────────────┤ │ HDR off, HDMI 120Hz │ Pure blacks — fine │ ├─────────────────────────────────┼────────────────────────┤ │ HDR on, DisplayPort 120Hz │ Pure blacks — fine │ ├─────────────────────────────────┼────────────────────────┤ │ Windows 10, same hardware/cable │ Pure blacks — fine │ ├─────────────────────────────────┼────────────────────────┤ │ Monitor screensaver dims panel │ Issue disappears │ └─────────────────────────────────┴────────────────────────┘ What was tried - edrPolicy: "never" — no effect - rgbRange: "Full" explicitly set — no effect - wideColorGamut disabled — no effect - Rolled back to Bazzite 43.20260309.1 (KWin 6.6.2-1, Mesa 26.0.1) — issue present - Rolled back to Bazzite 43.20260303 (KWin 6.6.1-1, Mesa 26.0.1) — issue present - wideColorGamut: false — no effect - Windows 10 on same hardware — no issue, confirming software cause Additional observation /sys/class/drm/card1-HDMI-A-2/hdr_output_metadata is empty despite HDR being active in KWin, suggesting HDR10 static metadata may not be reaching the kernel DRM layer for HDMI at 120Hz. Workaround Disabling HDR in Display Settings restores pure blacks immediately. --- -- You are receiving this mail because: You are watching all bug changes.
