Bug 493162

Summary:	Lowered Color Depth with lower refresh rate in HDR
Product:	[Plasma] kwin	Reporter:	hunder
Component:	colour-management	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	xaver.hugl
Priority:	NOR
Version First Reported In:	6.1.5
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	drm_info 60 Hz drm_info 120 Hz

Description hunder 2024-09-15 15:13:48 UTC

SUMMARY
In HDR Mode, when refresh rate is changed from native 120 Hz to a lower refresh rate the color depth gets lowered too. When in 120 Hz the color depth looks the same as when running Windows (10 Bit). With 60 Hz it looks like 6 Bit color depth.

STEPS TO REPRODUCE
1. HDR enabled and monitor set to native refresh rate
2. Lower refresh rate to something like 60 Hz 

OBSERVED RESULT
Really bad color banding, looks like 6 Bit color depth.

EXPECTED RESULT
Same color depth as native refresh rate, in this case it should be 10 Bit

SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux 
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.10.10-2-cachyos-lto (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X3D 8-Core Processor
Memory: 62.7 GiB of RAM
Graphics Processor: AMD Radeon RX 7900 XTX

Comment 1 Zamundaaa 2024-09-16 16:59:29 UTC

Please attach the output of drm_info, once for each mode

Comment 2 hunder 2024-09-16 18:09:30 UTC

Created attachment 173743 [details]
drm_info 60 Hz

Comment 3 hunder 2024-09-16 18:12:21 UTC

Created attachment 173744 [details]
drm_info 120 Hz

Comment 4 Zamundaaa 2024-09-16 20:02:49 UTC

There's no difference except for the refresh rate in the output configuration, so this is a driver bug. Please report it at https://gitlab.freedesktop.org/drm/amd/-/issues