Public bug reported:
### Hardware Setup
- **Laptop:** Lenovo ThinkPad P15v Gen 3 AMD (Type 21EM0016PB)
- **CPU / SoC:** AMD Ryzen 7 PRO 6850H (Rembrandt) with Radeon 680M
- **dGPU:** NVIDIA T1200 Laptop GPU
- **Dock:** Lenovo ThinkPad Thunderbolt 4 Workstation Dock (Type 40B0, Intel
Goshen Ridge JHL8440, Firmware v1.0.20 / NVM 44.83)
- **OS / Kernel:** Ubuntu 24.04.4 LTS, Kernel 7.0.0-30-generic (and reproduced
on 6.8.0)
- **Connected Peripherals:** 2x External Displays (DisplayPort MST), USB
Keyboard/Mouse (Logitech Lightspeed receiver), Audio, LAN.
---
### Problem Description
When connecting the ThinkPad Thunderbolt 4 Dock (40B0) to the AMD Rembrandt
USB4 host router (`1022:162e`), the dock enters an infinite connect/disconnect
flapping loop (every 2-3 seconds, failing over 100+ times per boot).
As a result, no USB3 tunnels or DisplayPort tunnels can be established. Mouse,
keyboard, and external monitors completely fail to work.
### Kernel Log (dmesg excerpt)
```text
thunderbolt 0-2: new device found, vendor=0x108 device=0x2031
thunderbolt 0-2: Lenovo ThinkPad Thunderbolt 4 Dock
usb 7-1: device not accepting address 28, error -71
thunderbolt 0000:68:00.5: 2: failed to enable TMU
thunderbolt 0000:68:00.5: 2: USB3 tunnel creation failed
thunderbolt 0000:68:00.5: 2:1: hop deactivation failed for hop 1, index 8
thunderbolt 0000:68:00.5: PCIe Down path activation failed: -107
thunderbolt 0000:68:00.5: 0:5 <-> 2:9 (PCI): activation failed
thunderbolt 0000:68:00.5: 2:9: PCIe tunnel activation failed, aborting
thunderbolt 0-2: device disconnected
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-7.0.0-30-generic 7.0.0-30.30~24.04.1
ProcVersionSignature: Ubuntu 7.0.0-30.30~24.04.1-generic 7.0.12
Uname: Linux 7.0.0-30-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sun Aug 30 16:47:11 2026
InstallationDate: Installed on 2023-09-13 (1082 days ago)
InstallationMedia: Ubuntu 22.04.3 LTS "Jammy Jellyfish" - Release amd64
(20230807.2)
MachineType: LENOVO 21EM0016PB
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-30-generic
root=/dev/mapper/vgubuntu-root ro quiet splash usbcore.autosuspend=-1
idle=nomwait processor.max_cstate=5 amdgpu.dcdebugmask=0x10
thunderbolt.host_reset=0 thunderbolt.clx=0
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
RelatedPackageVersions:
linux-restricted-modules-7.0.0-30-generic N/A
linux-backports-modules-7.0.0-30-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.29
SourcePackage: linux-hwe-7.0
UpgradeStatus: Upgraded to noble on 2024-09-16 (713 days ago)
dmi.bios.date: 05/26/2026
dmi.bios.release: 1.31
dmi.bios.vendor: LENOVO
dmi.bios.version: N3KET53W (1.31 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21EM0016PB
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.17
dmi.modalias:
dmi:bvnLENOVO:bvrN3KET53W(1.31):bd05/26/2026:br1.31:efr1.17:svnLENOVO:pn21EM0016PB:pvrThinkPadP15vGen3:rvnLENOVO:rn21EM0016PB:rvrNotDefined:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21EM_BU_Think_FM_ThinkPadP15vGen3:pfaThinkPadP15vGen3:
dmi.product.family: ThinkPad P15v Gen 3
dmi.product.name: 21EM0016PB
dmi.product.sku: LENOVO_MT_21EM_BU_Think_FM_ThinkPad P15v Gen 3
dmi.product.version: ThinkPad P15v Gen 3
dmi.sys.vendor: LENOVO
** Affects: linux-hwe-7.0 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
--
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Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2165852
Title:
[AMD Rembrandt + ThinkPad TB4 Dock 40B0] Infinite disconnect loop:
"failed to enable TMU" / "USB3 tunnel creation failed" without
thunderbolt.clx=0
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