SUMMARY Disabling KDE Plasma HDR on this OLED laptop when running in Hybrid GPU Mode causes a complete failure in display control. The screen brightness becomes permanently stuck at an uncontrollably high level. Furthermore, the display rendering is grossly incorrect. Light areas are blindingly intense, while dark areas are too dark, making the image look distorted and unusable. The system's brightness slider has zero effect. This critical issue only occurs in Hybrid GPU mode; using dGPU or iGPU-only modes (selecting it from the BIOS) works correctly after HDR is disabled. STEPS TO REPRODUCE 1. Ensure the laptop is running in the Hybrid GPU Mode (using both Intel iGPU and Nvidia dGPU). 2. Enable KDE Plasma HDR. 3. Calibrate the HDR settings. 4. Use the system with HDR enabled (brightness control works correctly here). 5. Disable KDE Plasma HDR. OBSERVED RESULT After disabling HDR in Hybrid GPU Mode: - The screen brightness immediately jumps to an uncomfortably high level. - The overall display appearance becomes visually distorted: lighter parts are extremely bright, and darker parts appear too dim. - The brightness slider in KDE has no effect on the screen brightness. EXPECTED RESULT After disabling HDR, the display should revert to standard SDR mode with: - Controllable brightness via the system slider. - Correct visual appearance and gamma. SOFTWARE/OS VERSIONS Operating System: CachyOS Linux KDE Plasma Version: 6.5.3 KDE Frameworks Version: 6.20.0 Qt Version: 6.10.1 Kernel Version: 6.18.0-rc7-1-cachyos-rc-lto (64-bit) | (Tried other available kernels, but they had the same issue.) Graphics Platform: Wayland Processors: 28 × Intel® Core™ i7-14700HX Memory: 32 GiB of RAM (31.1 GiB usable) Graphics Processor 1: Intel® Graphics Graphics Processor 2: NVIDIA GeForce RTX 5060 Laptop GPU Manufacturer: LENOVO Product Name: 83LY System Version: Legion 5 15IRX10 ADDITIONAL INFORMATION - The issue is specifically triggered by the HDR workflow: Standard SDR functionality was perfect before HDR was first enabled and calibrated on the system. The inability to return to controllable SDR mode only began after enabling, calibrating, and then disabling KDE Plasma HDR. - Re-enabling HDR immediately restores brightness control and corrects the display output. Disabling HDR again causes the issue again. - The issue does not occur when the laptop is switched to dGPU mode or iGPU-only mode via the BIOS. In these modes, disabling HDR works correctly. - The issue occurred on multiple operating systems, including CachyOS and OpenSUSE Tumbleweed. - A different kernel (linux-cachyos-lts) which failed to recognize the dGPU did not exhibit the issue (effectively acting as iGPU-only mode), further pointing to the hybrid setup being the root cause. Attempts to Fix (All Failed) The following troubleshooting steps were attempted without success in resolving the issue or restoring proper SDR functionality: - Rebooting the system. - Recalibrating HDR multiple times. - Creating a new user profile. - Switching the display protocol from Wayland to X11. - Reinstalling all packages. - Switching between various kernels. - Attempting a "clean" disable: Switching the BIOS to dGPU or iGPU-only mode (where SDR works correctly), ensuring HDR was disabled, reinstalling all packages, rebooting, and then switching the BIOS back to Hybrid Mode. The issue immediately returned upon re-entering Hybrid Mode.
Please attach the output of drm_info and kscreen-doctor -o, once for HDR enabled and once for HDR disabled. The output of drm_info for each of - iGPU mode - dGPU mode - hybrid GPU mode would also be interesting, I wonder what the difference could be
Created attachment 187354 [details] drm_info and kscreen-doctor -o outputs for each mode Here are drm_info and kscreen-doctor -o outputs for each mode. 1. Hybrid Mode HDR Off (Where the issue happens) 2. Hybrid Mode HDR On 3. dGPU Mode HDR Off 4. dGPU Mode HDR On 5. iGPU-Only Mode HDR Off 6. iGPU-Only Mode HDR On I restarted my PC each time I enable or disable HDR. Since this is too long, I used markdown syntaxes, so you guys can view this in a markdown viewer or easily find each mode by typing ## into the find tool in a text editor.
As expected, "dGPU Mode" means the mux is switched to the dedicated GPU, while both hybrid and iGPU mean it's switched to the internal GPU. I can't explain why the issue wouldn't happen in iGPU mode, but this is definitely a driver bug, according to the drm_info output, KWin does turn off HDR. You can report it at https://gitlab.freedesktop.org/drm/i915/kernel/-/issues As for why it happened only after you enabled HDR, did you perhaps synchronize settings to SDDM? If you disable HDR and then go into the SDDM settings page and "Apply Plasma Settings" there, does a reboot fix the problem? Also, why do you want to avoid leaving HDR on? The bug should be fixed either way ofc, but if there's an issue preventing you from always using HDR, I'd like to know about that as well.
Yes, I did synchronize settings to SDDM. And yes, it did fix after disabling HDR, synchronizing the settings again, and then rebooting. As for why I want to disable HDR, It gives color banding on regular content. It mostly disappears when I choose 'prefer color accuracy' option. But I can still see color banding on some stuff like dark videos or if I'm looking for them. I thought it's normal since HDR on Windows does the same. So I wanted to disable HDR when I'm doing regular stuff and only enable it when I need HDR. Thanks for your help. I will try to report the bug to the link you provided.
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