RTX 4090 [nvidia-open 610.43.02]: HDMI 2.1 FRL rate mis-selected on sink power-cycle — 4K@143.86/120/100 pruned to TMDS until reboot (KDE Wayland)

RTX 4090 [nvidia-open 610.43.02]: HDMI 2.1 FRL rate mis-selected on sink power-cycle — 4K@143.86/120/100 pruned to TMDS until reboot (KDE Wayland)

System

• GPU: RTX 4090 (AD102) · driver 610.43.02 open · kernel 7.0.12 (CachyOS)
• KWin 6.6.5 / Plasma 6.6.5, Wayland
• Display: Samsung QN90B 43" (HDMI 2.1 FRL, VRRmax 144, DSC 1.2a) on HDMI-A-1
• Connector NOT force-enabled (no video=HDMI-A-1:e) — so this is not #1084.

Summary

Cold boot trains FRL and 3840x2160@143.86 (VRR-derived) works. After the TV is
physically powered OFF and back ON during a running session, FRL is mis-selected
on re-detect: link drops to TMDS and every >594 MHz mode (4K@100/120/143.86) is
pruned — only 4K@60 remains. Full reboot restores it. Windows 11 on the same
hardware recovers without reboot.

Proof it is driver-side

• Raw EDID byte-identical good vs bad (cmp clean, product code unchanged) → not the EDID.
• With the helper daemon stopped, kscreen-doctor -o itself drops 4K>60 → mode list is from the driver, not KWin. HDR on/off does not change the list.
• nvidia-bug-report in the bad state reports protocol : TMDS.
• No userspace recovery: KMS re-modeset (rejected — single output) and DPMS off/on do not re-train; only reboot / another physical power-cycle does.

force_frl_rate gradient (the bug is in FRL rate selection)

/sys/module/nvidia_modeset/parameters/force_frl_rate, retested per value (reboot + power-cycle):

Forcing the rate deterministically changes the outcome, and none restore the
VRR-derived 4K@143.86 on hotplug → points at the FRL rate / VRR-mode selection
on the hotplug re-detect path.

Repro

1. Boot → 4K@143.86 works.
2. Power off TV, wait ~10s, power on.
3. 4K@100/120/143.86 gone, stuck at 4K@60 until reboot (non-deterministic).

Evidence

GOOD/BAD display-state dumps + both raw EDIDs (byte-identical):
https://gist.github.com/filipemendespi/dd6c1db5ec179b606667638a6a927567
(EDIDs are base64; base64 -d FILE.b64 > FILE)
Full nvidia-bug-report.log.gz (captured in the BAD state, shows protocol : TMDS)
available privately on request — withheld here as it contains host/network identifiers.

Start by reproducing the HDMI-A-1 power-cycle sequence and compare the supplied good and bad state dumps and raw EDIDs. Inspect the nvidia_modeset force_frl_rate results and the bad-state nvidia-bug-report showing TMDS; done means hotplug reselects FRL and restores the 4K@100/120/143.86 modes without reboot.