## Update: undocked-boot and USB-C port control tests on 7.0.0-28 I performed a controlled reboot on 2026-07-21 with the dock disconnected. I waited until the graphical desktop was running before connecting the same dock, cable, two DisplayPort monitors, and peripherals.
The undocked boot did not produce the previously observed boot-time messages: - `failed to allocate DP resource for port 7` - `DMUB notification skipped due to no handler` - `DM_MST: Differing MST start` However, the post-login result depended on which laptop USB-C port was used. ### Laptop USB-C port 1 → dock rear/upstream port: failed At 09:35:56, the connection failed during the initial USB setup, before the dock, Thunderbolt topology, or displays could enumerate: ```text usb 8-1: new high-speed USB device number 2 using xhci_hcd usb 8-1: Device not responding to setup address. usb 8-1: Device not responding to setup address. usb 8-1: device not accepting address 2, error -71 No subsequent Thunderbolt, USB4, or DP MST topology appeared. Disconnecting the cable produced no device-removal event, consistent with the device never completing enumeration. ### Laptop USB-C port 2 → dock front USB-C port: no upstream event This produced no USB, USB4, Thunderbolt, or DRM hot-plug event. All external DP connectors remained disconnected. This is consistent with the dock’s front USB-C port being downstream/peripheral-facing rather than its host/upstream port. ### Laptop USB-C port 2 → dock rear/upstream port: succeeded Using the same dock, cable, displays, peripherals, running kernel, and desktop session, the dock enumerated through the second laptop USB-C port: [drm] DM_MST: starting TM [drm] DM_MST: DP14, 2-lane link detected usb 7-1: new SuperSpeed Plus Gen 2x1 USB device number 2 usb 7-1: New USB device found, idVendor=8087, idProduct=0b40 usb 7-1: Product: USB3.0 Hub The dock MCU, USB 2/3 hubs, Realtek Ethernet, dock audio, and attached Logitech C270 webcam all enumerated. Ethernet obtained carrier. Display topology discovery logged one error: amdgpu 0000:33:00.0: [drm] *ERROR* Sending link address failed with -5 The driver recovered without disconnecting the dock: [drm] Synaptics Cascaded MST hub [drm] Synaptics Cascaded MST hub [drm] MST_DSC Send DSC enable to synaptics [drm] MST_DSC Send DSC enable to synaptics Both external screens then turned on. The final DRM connector state showed DP-9 and DP-10 connected. This successful attempt did not produce: - USB error -71 - dcn31_program_compbuf_size warning - update_dpia_stream_allocation_table warning - GNOME/Mutter atomic-commit failure - complete dock disconnect/reconnect ## Interpretation These results do not support a purely boot-ordering or purely AMDGPU explanation. Booting undocked avoids the previously observed boot-time DP- resource/MST-ordering messages, but a normal post-login connection can still fail at the earliest USB setup stage on one laptop USB-C path. At that point, Thunderbolt and AMDGPU have not yet discovered the dock. The same equipment works minutes later through the second laptop USB-C port, although that successful path still produces a transient recoverable AMDGPU MST link-address error. The normal-use failure therefore appears port/path-sensitive and may involve the platform USB/XHCI/USB4 path, firmware, signal integrity, or hardware. The available evidence does not yet identify which component is responsible. Separately, the trigger_hpd_mst_set kernel oops remains a definite AMDGPU kernel-driver defect. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2160619 Title: USB-C/USB4 dock path instability: port-dependent USB error -71, Thunderbolt disconnects, and AMDGPU DP MST failures To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2160619/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
