Public bug reported:
On a Lenovo laptop with AMD Rembrandt / Radeon 680M, external monitors
connected through a Lenovo ThinkPad Universal Thunderbolt 4 Smart Dock often
stay dark when the system is booted while already docked. Kernel logs show
repeated USB enumeration failures on the dock path, Thunderbolt dock
connect/disconnect, amdgpu DP AUX/DPCD/MST link failures, and a warning
in dcn31_program_compbuf_size. A manual MST reprobe via
/sys/kernel/debug/dri/0000:33:00.0/amdgpu_dm_trigger_hpd_mst caused a
reproducible amdgpu kernel oops in trigger_hpd_mst_set.
```
## Reproduction steps to paste
```text
1. Connect the laptop to a Lenovo ThinkPad Universal Thunderbolt 4 Smart Dock
with two external DP monitors attached.
2. Boot the machine while already docked.
3. Observe that the external monitors sometimes remain dark.
4. Check kernel logs for repeated usb 8-1 enumeration failures, Thunderbolt
disconnects, and amdgpu MST / AUX / DPCD errors.
Additional diagnostic reproduction:
5. When the docked displays are in a working MST state, write "1" to
/sys/kernel/debug/dri/0000:33:00.0/amdgpu_dm_trigger_hpd_mst.
6. Observe a kernel oops in trigger_hpd_mst_set [amdgpu].
```
## Expected result
```text
The dock should enumerate cleanly during boot, both external monitors should
come up reliably, and an MST hotplug reprobe should not crash the kernel.
```
## Actual result
```text
During docked boot, the dock path repeatedly fails USB enumeration,
Thunderbolt disconnects after appearing, amdgpu DP MST link setup fails, and
the external monitors may remain dark. A manual MST reprobe can trigger a
kernel oops in amdgpu.
```
## High-signal details to include
- Kernel: `7.0.0-27-generic`
- GPU: `AMD Rembrandt / Radeon 680M`
- BIOS: `R22ET81W (1.51)`, `2026-04-10`
- Dock: `Lenovo ThinkPad Universal Thunderbolt 4 Smart Dock`
- No dock firmware update was offered by `fwupdmgr`
- No system firmware or EC update was pending
## Key log lines to mention
These are the most important patterns:
amdgpu ... [drm] DPIA AUX failed on 0x2c0(1), error 7
thunderbolt 0-2: device disconnected
amdgpu ... [drm] *ERROR* dpcd_set_link_settings ...
amdgpu ... [drm] *ERROR* Sending link address failed with -5
WARNING: ... dcn31_program_compbuf_size
[drm:trigger_hpd_mst_set [amdgpu]] *ERROR* DM_MST: Failed to detect dc link!
BUG: unable to handle page fault ...
RIP: trigger_hpd_mst_set+0x13b/0x1b0 [amdgpu]
```
## Files prepared locally
- Main report:
[UBUNTU_BUGREPORT_DP_DOCK_MST.md](/home/tstocke/gitlab.ethz.ch/eth-config-tool/UBUNTU_BUGREPORT_DP_DOCK_MST.md)
- Filing guide:
[UBUNTU_BUGREPORT_DP_DOCK_MST_FILING.md](/home/tstocke/gitlab.ethz.ch/eth-config-tool/UBUNTU_BUGREPORT_DP_DOCK_MST_FILING.md)
## Suggested filing workflow
Run:
```bash
ubuntu-bug linux
```
Then in the bug text:
1. Use the bug title from this file.
2. Paste the short summary.
3. Paste the reproduction steps.
4. Paste expected and actual result.
5. Attach or paste the contents of `UBUNTU_BUGREPORT_DP_DOCK_MST.md`.
## Optional extra attachments
If Apport does not automatically gather enough information, attach the output
of:
```bash
uname -a
journalctl -b -k
sudo lspci -nnk
sudo fwupdmgr get-devices
sudo fwupdmgr get-updates
sudo boltctl list
sudo cat /sys/kernel/debug/dri/0000:33:00.0/amdgpu_mst_topology
```
## Note
The `trigger_hpd_mst_set` reprobe was used only as a diagnostic step. It
should not be treated as a safe workaround, because it caused a kernel oops on
this system.
```text
usb 8-1: Device not responding to setup address
usb 8-1: device not accepting address ..., error -71
thunderbolt 0-2: Lenovo ThinkPad Universal Thunderbolt 4 Smart Dock
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-7.0.0-27-generic 7.0.0-27.27
ProcVersionSignature: Ubuntu 7.0.0-27.27-generic 7.0.6
Uname: Linux 7.0.0-27-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Tue Jul 14 14:58:10 2026
InstallationDate: Installed on 2025-03-12 (489 days ago)
InstallationMedia: Ubuntu 24.04.2 LTS "Noble Numbat" - Release amd64 (20250215)
MachineType: LENOVO 21CRS08P00
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-27-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-05-08 (67 days ago)
dmi.bios.date: 04/10/2026
dmi.bios.release: 1.51
dmi.bios.vendor: LENOVO
dmi.bios.version: R22ET81W (1.51 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21CRS08P00
dmi.board.vendor: LENOVO
dmi.board.version: SDK0K17763 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.33
dmi.modalias:
dmi:bvnLENOVO:bvrR22ET81W(1.51):bd04/10/2026:br1.51:efr1.33:svnLENOVO:pn21CRS08P00:pvrThinkPadT14sGen3:rvnLENOVO:rn21CRS08P00:rvrSDK0K17763WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21CR_BU_Think_FM_ThinkPadT14sGen3:pfaThinkPadT14sGen3:
dmi.product.family: ThinkPad T14s Gen 3
dmi.product.name: 21CRS08P00
dmi.product.sku: LENOVO_MT_21CR_BU_Think_FM_ThinkPad T14s Gen 3
dmi.product.version: ThinkPad T14s Gen 3
dmi.sys.vendor: LENOVO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
** Attachment added: "UBUNTU_BUGREPORT_DP_DOCK_MST.md"
https://bugs.launchpad.net/bugs/2160619/+attachment/5981810/+files/UBUNTU_BUGREPORT_DP_DOCK_MST.md
--
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:
amdgpu: DP MST via Lenovo ThinkPad Universal Thunderbolt 4 Smart Dock
fails at boot and trigger_hpd_mst_set causes kernel oops:set nonumbers
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
