[Nobara 43 / RTX 5070] DisplayPort via USB-C dock not working — ucsi_acpi unknown error 256 + Billboard Device not bound

[Sebastien2]

Hello there,

I’ve a problem with a dock, this is a brief descrition (with some help by an AI):

Hardware:

• Framework Laptop 16 (AMD Ryzen AI 300 Series)
• NVIDIA GeForce RTX 5070 Graphics Module
• BIOS: 03.06 (04/23/2026)
• Dock: UGREEN CM843 (USB-C, VIA Labs controller)

Software:

• Nobara 43
• Kernel: 7.0.9-200.nobara.fc43.x86_64
• NVIDIA driver: 595.71.05 (Open Kernel Module)
• nvidia-drm.modeset=Y, fbdev=Y

---

Problem

Monitors connected via DisplayPort on the UGREEN CM843 dock are not detected by the OS. The dock’s USB functions work correctly (Ethernet via RTL8153, USB hubs, keyboard, mouse), but no display output is negotiated on any DP port.

The issue occurs on both:

• A USB-C expansion card slot (lateral port #1)
• The USB-C port on the rear of the RTX 5070 graphics module

---

Diagnosis

1. ucsi_acpi initialization failure

[3.084958] ucsi_acpi USBC000:00: unknown error 256
[4.274929] ucsi_acpi USBC000:00: unknown error 256
[4.837177] ucsi_acpi USBC000:00: unknown error 256

The UCSI controller fails to initialize at boot, which prevents DisplayPort Alt Mode negotiation on all USB-C ports.

2. USB Billboard Device with no driver

The dock correctly announces DisplayPort Alt Mode capability via Billboard devices:

usb X-X.X: Product: USB Billboard Device
usb X-X.X: Manufacturer: VIA Labs, Inc.
Driver=(none)

Two Billboard devices appear (one per DP output on the dock), but no driver binds to them.

3. typec_displayport and typec_nvidia not auto-loaded

These modules are present in the kernel tree but not loaded by default:

find /lib/modules/7.0.9-200.nobara.fc43.x86_64 -name "*.ko*" | grep typec
→ typec_displayport.ko.zst
→ typec_nvidia.ko.zst

After manually loading them (modprobe typec_displayport && modprobe typec_nvidia), the typec devices appear:

ls /sys/bus/typec/devices/
→ port0.0  port0.1  port1.0  port2.0  port3.0  port3.1

Altmodes show active=yes and SVID ff01 (DisplayPort) on ports 0.1, 1.0, 2.0, 3.1.

4. typec_displayport driver does not bind

Despite the driver being loaded and altmodes showing active=yes with the correct SVID, no driver binds to any altmode device:

for dev in /sys/bus/typec/devices/port*/; do
  readlink $dev/driver 2>/dev/null || echo "pas de driver"
done
→ pas de driver (×6)

Manual bind attempt fails:

echo "port0.1" | sudo tee /sys/bus/typec/drivers/typec_displayport/bind
→ tee: /sys/bus/typec/drivers/typec_displayport/bind: Aucun périphérique de ce type

The device type is typec_port_alternate_mode — it appears typec_displayport does not bind to port-side altmodes, only to partner-side altmodes. But since UCSI fails, no partner devices are registered.

5. DRM connectors all disconnected

card2-DP-1 through card2-DP-8: disconnected
card1-DP-9: disconnected

Despite the NVIDIA Open KMS driver being loaded correctly (nvidia-drm 0.0.0 on minor 1), all DP connectors report disconnected.

There is also this message at boot:

nvidia 0000:c2:00.0: [drm] Cannot find any crtc or sizes

---

Summary of root cause

The ucsi_acpi USBC000:00: unknown error 256 prevents the UCSI stack from registering USB-C partner devices. Without partner devices, typec_displayport cannot bind, DisplayPort Alt Mode is never negotiated, and the dock’s DP outputs are invisible to the DRM subsystem.

This affects all USB-C ports on the system (both expansion card slots and the RTX 5070 rear port).

---

What I have tried

• Verified BIOS is up to date (03.06, April 2026) — no UCSI-related fix found in changelog
• NVIDIA Open Kernel Modules confirmed active (595.71.05)
• nvidia-drm.modeset=1 and fbdev=1 confirmed active
• Secure Boot is not interfering
• Manually loaded typec_displayport and typec_nvidia — altmodes appear but driver does not bind
• Manual bind via sysfs fails with “no such device”
• Tested dock on both lateral USB-C slot and rear RTX 5070 USB-C port — same result

---

Questions

1. Is the ucsi_acpi unknown error 256 on Ryzen AI 300 + this BIOS version a known issue? Is there a kernel parameter or quirk to work around it?
2. Is there a way to force UCSI reinitialization or substitute a different driver (e.g. cros_ec_ucsi)?
3. Should typec_displayport and typec_nvidia be loaded by default on this hardware? Is there a udev rule or module configuration that handles this?
4. Has anyone successfully used a USB-C dock with DP output on Framework 16 + RTX 5070 under Linux?

---

System info

uname -r        → 7.0.9-200.nobara.fc43.x86_64
dmidecode bios  → 03.06 / 2026-04-23
nvidia driver   → 595.71.05 Open KM
lsmod typec     → typec_ucsi, typec, thunderbolt (typec_displayport loaded manually)
/sys/class/typec → port0..port4 with partner, cable, plug entries

Full dmesg available on request.

Thank you by advance,

Seb