https://bugs.kde.org/show_bug.cgi?id=512959
Bug ID: 512959
Summary: Cannot Revert to SDR: Display Unusable After Disabling
HDR in Hybrid GPU Setup
Classification: Plasma
Product: kwin
Version First 6.5.3
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: critical
Priority: NOR
Component: colour-management
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
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.
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