BC-250/UGREEN Active 8k60 Adapter: HDMI VRR over DP->HDMI PCON adapter only partially working (FreeSync-only, not generic HDMI VRR)

[baltimoresports]

HDMI VRR over DP->HDMI PCON adapter only partially working (FreeSync-only, not generic HDMI VRR)

Summary

VRR over a DP->HDMI PCON adapter doesn't seem to fully work on the ogc-7.2.y kernel. Comparing against CachyOS's kernel (which works with the same hardware/adapter), it looks like ogc-7.2.y has the CH7218 whitelist patch but not the broader "generic" HDMI VRR support that doesn't depend on the display advertising FreeSync.

What I found comparing the two kernel sources

• ogc-7.2.y (this repo's OpenGamingCollective/linux): has DP_BRANCH_DEVICE_ID_2B02F0 (Chrontel CH7218) in dm_is_freesync_pcon_whitelist() in amdgpu_dm_helpers.c, but that only gates FREESYNC_TYPE_PCON_IN_WHITELIST (FreeSync-over-HDMI passthrough).
• CachyOS's 7.2/hdmi branch (cachyos/linux) additionally has freesync_on_desktop wired into info_packet.c, plus a DC_OVERRIDE_PCON_VRR_ID_CHECK debug flag in amd_shared.h — this looks like the piece that enables VRR regardless of whether the sink advertises FreeSync.

Relevant upstream series this traces back to: https://www.mail-archive.com/amd-gfx@lists.freedesktop.org/msg137195.html

Hardware

BC-250 (AMD Oberon APU) + UGREEN DP134 (mfr part 85564) DP->HDMI adapter. Confirmed on Bazzite stable (7.2.0-ogc6.1.fc44, 44.20260825) that modinfo amdgpu shows no hdmi_vrr_desktop_mode/allm params, consistent with the above.

Question

Is the broader HDMI VRR support (the freesync_on_desktop/VTEM info-packet piece) something that's planned to be pulled into ogc-7.2.y, or is there a reason it's been left out so far? Happy to help test if useful — CachyOS's 7.2/hdmi branch looks like it'd be a reasonable reference for what to backport.

[baltimoresports]

• #3634 — Feature request, CH7218 whitelist patch provided (the original report): Feature Request: Add Chrontel CH7218 to the VRR PCON whitelist (patch provided) ublue-os/bazzite#3634
• #4532 — VRR still broken with the UGREEN adapter (the one you commented on): VRR doesn’t work when using a UGREEN DisplayPort-to-HDMI cable. ublue-os/bazzite#4532
• CachyOS Commit ddf48d9: CachyOS/linux@ddf48d9

[baltimoresports]

Still seeing this on latest stable — dug a bit further and wanted to share what I found.

Problem: VRR doesn't negotiate over your BC-250's DP→HDMI (UGREEN 85564/CH7218) adapter on Bazzite — TV supports FreeSync, adapter chip is whitelisted, but the kernel still reports vrr_range: 0/0.

What CachyOS does differently, specifically:

1. freesync_on_desktop support in info_packet.c — keeps HDMI VRR signaling active continuously (even at a fixed refresh rate), rather than only toggling it during actual refresh-rate changes. HDMI doesn't guarantee seamless VRR transitions the way DisplayPort does, so many TVs glitch/blank if VRR toggles on and off — this patch avoids that by leaving VRR "on" at the signal level all the time once negotiated.

2. DC_OVERRIDE_PCON_VRR_ID_CHECK debug flag in amd_shared.h — lets the driver skip the PCON chip allow-list check entirely, useful for testing adapters not yet whitelisted.

3. Broader HDMI VRR enablement — commits like Enable HDMI VRR, Reintroduce VTEM info frame, and Rename PCON adaptive sync types, which together implement generic HDMI VRR negotiation that doesn't require the display to advertise FreeSync specifically — only the HDMI Forum's standard VRR signaling.

Bazzite's kernel only has the CH7218 whitelist entry (which gates FREESYNC_TYPE_PCON_IN_WHITELIST — FreeSync-over-HDMI only) — none of the three items above. That's the concrete gap: even with a whitelisted adapter and a FreeSync-capable TV, Bazzite's driver has no code path to actually keep VRR signaling active or negotiate it outside the narrow FreeSync passthrough case.

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System:

• uname -r: 7.2.1-ogc3.1.fc44.x86_64 (latest stable as of writing)
• Hardware: BC-250 (AMD Oberon APU)
• Adapter: UGREEN DP134 / mfr part 85564 (same as [#3634](Feature Request: Add Chrontel CH7218 to the VRR PCON whitelist (patch provided) ublue-os/bazzite#3634))
• TV: Hisense U6 Pro (2026) — supports AMD FreeSync Premium Pro per spec sheet

Works fine on CachyOS with the same hardware/adapter/TV, just not on Bazzite.

Checked the actual negotiated VRR state via debugfs:

$ sudo cat /sys/kernel/debug/dri/0000:01:00.0/DP-1/vrr_range

Min: 0
Max: 0

Driver reports zero VRR range on this connection, despite the TV supporting FreeSync.

Comparing OpenGamingCollective/linux (tag v7.2.1-ogc3, what this kernel is built from) against cachyos/linux (7.2/hdmi, where it works): both have the CH7218 PCON whitelist entry from #3634, but CachyOS additionally carries freesync_on_desktop support and a DC_OVERRIDE_PCON_VRR_ID_CHECK debug flag that OGC doesn't have. That looks like the actual gap — the whitelist alone doesn't seem to be enough here. Also confirmed no hdmi_vrr_desktop_mode/allm params via modinfo, consistent with this.

Disclaimer: Used Claude to help troubleshoot and write response.