Bug 478658

Summary:	LG 27gl850 is falsely detected as Vrr: incapable
Product:	[Plasma] kwin	Reporter:	Soukyuu <chrno-sphered>
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	nate, vlad.zahorodnii, xaver.hugl
Priority:	NOR	Keywords:	qt6
Version:	5.90.0
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	output of kscreen-doctor --outputs output of drm_info

Description Soukyuu 2023-12-17 18:11:24 UTC

Created attachment 164256 [details]
output of kscreen-doctor --outputs

SUMMARY
***
This is the first time I'm trying to get VRR working on linux and wayland, so I'm not sure where to look.

I have an LG 27gl850 Monitor which is Freesync capable according to AMD itself [1]. I read there is supposed to be a toggle to enable VRR for the monitor in display settings, but there is none. kscreen-doctor reports "Vrr: incapable" both over HDMI and DisplayPort (via HP Thunderbolt Dock G4). The monitor OSD displays "Adaptive-Sync: ON".
***


STEPS TO REPRODUCE
1. Connect via DisplayPort (or HDMI)
2. Make sure FreeSync Premium is enabled in Monitor internal settings (Menu -> Game Adjust -> Adaptive-Sync -> On)
3. Run kscreen-doctor --outputs

OBSERVED RESULT

The monitor is listed as "Vrr: incapable" both via HDMI and DisplayPort

EXPECTED RESULT

The monitor should be listed as "Vrr: capable/enabled", I guess?

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: arch linux
KDE Plasma Version: 5.90 (Beta 1)
KDE Frameworks Version: 5.246.0
Qt Version: 6.6.1

ADDITIONAL INFORMATION
I am not sure if this is something on kscreen or drm side, attaching both output of kscreen-doctor and drm_info while the monitor is attached via DisplayPort.

[1] https://www.amd.com/en/products/graphics/technologies/freesync/monitors.html (page 3 if you filter by manufacturer -> LG)

Comment 1 Soukyuu 2023-12-17 18:11:43 UTC

Created attachment 164257 [details]
output of drm_info

Comment 2 Zamundaaa 2023-12-20 23:13:57 UTC

KWin doesn't show whether or not the screen itself is capable of VRR (though perhaps we should do that too), it shows whether or not the driver can do VRR on it.

> via HP Thunderbolt Dock G4
That's the problem: AMD (currently) doesn't support VRR with any docks except the Steam Deck Dock, IIRC because docks are just so broken in general that it's hard to give a general guarantee that it works without problems.
You could open an issue at https://gitlab.freedesktop.org/drm/amd/-/issues about changing that for your dock as well, or giving an option to override the driver's default setting for this. Until that's resolved though, your only choice is to get a USB C -> DisplayPort cable and connect the monitor directly to your laptop.

Comment 3 Soukyuu 2023-12-21 07:02:01 UTC

I'm not sure anything usb-c will work. This is a framework laptop, so all it has for ports are 4x usb-c which are then filled with "expansion cards" that are basically usb-to-x adapters. The "HDMI" port Ialso tried is one such adapter and VRR doesn't work either. On my old 2500U based laptop with a native HDMI port, VRR works.

I opened a bug over at the drm repo [1], but not really holding my breath.

[1] https://gitlab.freedesktop.org/drm/amd/-/issues/3059

Comment 4 Zamundaaa 2023-12-21 17:02:02 UTC

USB C -> (single!) DisplayPort isn't an adapter. USB C can directly output DisplayPort, and I'm using a USB C -> DisplayPort cable with my own Framework laptop, where VRR works.