https://bugs.kde.org/show_bug.cgi?id=526998
Bug ID: 526998
Summary: HDR prevents direct scanout on NVIDIA despite DRM
color-pipeline support in newer drivers
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 197049
--> https://bugs.kde.org/attachment.cgi?id=197049&action=edit
qdbus6 org.kde.KWin /KWin supportInformation
Product: KWin
Component: DRM/Wayland
Version: 6.7.91 (Plasma 6.8 Beta 2)
Platform: Arch Linux
Severity: Normal
SUMMARY
Enabling HDR in KDE Plasma prevents direct scanout of fullscreen games on
NVIDIA, despite the newer NVIDIA drivers now supporting DRM color pipelines.
With HDR disabled in Plasma Display Configuration, direct scanout works
correctly. However, enabling HDR causes KWin to composite the same fullscreen
game, regardless of whether HDR is enabled or disabled within the game itself.
I'm running NVIDIA driver 615.78.08, which exposes DRM color-pipeline support.
The following command confirms it is enabled:
$ cat /sys/module/nvidia_drm/parameters/color_pipeline
Y
Since the previous lack of DRM color-pipeline support was identified as a
limitation for HDR direct scanout on NVIDIA, I would like to know whether KWin
can now take advantage of this functionality or whether another limitation
remains.
STEPS TO REPRODUCE
Start a KDE Plasma Wayland session on an NVIDIA GPU with an HDR-capable
monitor.
In Display Configuration, select Prefer efficiency under color accuracy.
Disable HDR in Plasma.
Launch Gears of War: E-Day in fullscreen through Steam/Proton, without
Gamescope.
Verify that direct scanout is working using KWin's showcompositing debug
effect.
Enable HDR in Plasma Display Configuration.
Relaunch the same game and check the debug effect.
Repeat with in-game HDR enabled and disabled.
OBSERVED RESULT
Plasma HDR off, in-game HDR off: Direct scanout works.
Plasma HDR on, in-game HDR off: Direct scanout does not work.
Plasma HDR on, in-game HDR on: Direct scanout does not work.
Whenever HDR is enabled in Plasma, KWin's showcompositing effect continues to
indicate compositing.
Disabling HDR in Plasma restores direct scanout.
EXPECTED RESULT
Fullscreen games should be eligible for direct scanout with HDR enabled when
the graphics driver and DRM color pipeline support the required color
transformations.
Enabling HDR in Plasma should not necessarily prevent direct scanout when
compatible hardware color-processing capabilities are available.
SOFTWARE/OS VERSIONS
Operating System: CachyOS (Arch Linux)
KDE Plasma Version: 6.7.91 (6.8 Beta 2)
Graphics Platform: Wayland
Linux Kernel: 7.2.9-cachyos
GPU: NVIDIA GeForce RTX 4080
NVIDIA Driver: 615.78.08 (proprietary)
Monitor: LG 45GX950A OLED
Connection: HDMI 2.1
Resolution: 5120 × 2160
Refresh Rate: 165 Hz
ADDITIONAL INFORMATION
Earlier discussions about HDR direct scanout on NVIDIA identified the lack of
DRM color-pipeline support in the proprietary NVIDIA driver as a blocker.
However, recent NVIDIA drivers now expose this functionality, and
nvidia_drm.color_pipeline is enabled on my system.
Despite this, HDR still prevents direct scanout in Plasma 6.8 Beta 2.
Does KWin currently support using NVIDIA's newly available DRM color pipelines
for HDR direct scanout? If so, is there an additional limitation or missing
capability preventing it from working?
I understand that the driver reporting color-pipeline support does not
necessarily guarantee support for every required color transformation.
I can provide drm_info, kscreen-doctor -o, and KWin's supportInformation output
if needed.
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