[Bug 2155195] Re: [Panther Lake/xe] DisplayPort-over-Thunderbolt external monitor not detected at cold boot (regression in linux 7.0.0-22)

Second hardware combo hitting the same failure class System: - ThinkPad P1 Gen9 (21UFS0KC00), BIOS N4SET30W 1.09 - Lenovo ThinkPad Thunderbolt 5 Smart Dock 7500 - 40BA (not Dell TB4 — different dock vendor/gen, same failure class) - 3 monitors: Dell U2415 (1920x1200), LG HDR 4K (3840x2160), built-in eDP (3200x2000) - Kernel 7.0.0-34-generic (Linux Mint 22.2 / Ubuntu 24.04 base, Cinnamon 6.6.4) - Intel Panther Lake, xe driver — same platform as the original report Unlike the original report (cold-boot-only), I have two additional 100%-reproducible triggers on this hardware, both ending in a genuine kernel-level hang (Xorg goes into uninterruptible D state, unrecoverable without a hard reset): 1. Opening Cinnamon's Display Settings applet with the dock's MST-tunneled monitors attached, changing any setting and applying it 2. The screensaver/DPMS wake-from-idle cycle. Both produce this signature in dmesg, with an escalating pre-freeze pattern before the hard hang: xe 0000:00:02.0: [drm] *ERROR* [CONNECTOR:...] Failed to get ACT after 3000 ms workqueue: intel_atomic_cleanup_work [xe] hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND workqueue: intel_atomic_cleanup_work [xe] hogged CPU for >10000us 5 times, ... workqueue: intel_atomic_cleanup_work [xe] hogged CPU for >10000us 11 times, ... workqueue: intel_atomic_cleanup_work [xe] hogged CPU for >10000us 19 times, ... (count keeps climbing — 4, 5, 7, 11, 19, 35, 67, 131... — until hard freeze) Additional isolation donet: - Not NVIDIA-related: this is a muxless hybrid laptop; NVIDIA never drives any display output regardless of driver state. Confirmed across nouveau, the -open driver, and the closed nvidia-driver-610 package (which actually refuses to load its kernel module on this GPU at all — NVRM: ... requires use of the NVIDIA open kernel modules). xe is the only driver touching any output in every configuration tested. Rules out NVIDIA as a contributing factor. - Cross-hardware control test: connected the identical dock model to a completely different laptop (ThinkPad P1 Gen4i, Tiger Lake, hardware-MUXed NVIDIA driving all outputs, i915 not even loaded). Zero ACT/link-training/atomic-cleanup-workqueue errors across multiple dock hotplug/replug cycles. This isolates the fault to the xe/Panther Lake/muxless side of the pairing, not the dock or monitors. - Also observed: after a wedge, only a full Thunderbolt tunnel teardown+rebuild that lands on a new enumeration path (e.g. thunderbolt port 1-1 → 1-3) clears the wedged state (a same-port reconnect reusing the existing tunnel does not recover it). This is consistent with your root-cause note that the tunnel isn't recreated once torn down early, in my case it's torn down by the driver getting into a bad MST/ACT state post-boot, not just at cold boot, but the underlying "xe doesn't cleanly re-establish the DP tunnel" mechanism looks like the same bug surfacing on a different trigger. Is this related? https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/9421 -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2155195 Title: [Panther Lake/xe] DisplayPort-over-Thunderbolt external monitor not detected at cold boot (regression in linux 7.0.0-22) Status in linux package in Ubuntu: Fix Committed Bug description: Ubuntu release: Ubuntu 26.04 LTS (resolute) [lsb_release -rd] Kernel package: linux-image-7.0.0-22-generic 7.0.0-22.22 version_signature: Ubuntu 7.0.0-22.22-generic 7.0.0 What I expected: On boot, an external monitor connected via a Dell Thunderbolt 4 dock (DisplayPort output) should be detected and lit, as it was on kernel 7.0.0-15-generic. What happened instead: After updating to 7.0.0-22-generic, the external monitor is not detected on a cold boot. All other dock functions work normally (USB keyboard/mouse, YubiKey, Gigabit Ethernet), and the same dock + cable + monitor work in Windows on the same machine. The internal panel (eDP-1) works. All /sys/class/drm/card1-DP-*/status read "disconnected"; only eDP-1 is connected. Root cause (boot-time ordering race in DisplayPort-over-Thunderbolt tunneling): The Thunderbolt connection manager sets up and tears down the DP tunnel ~83s BEFORE the xe display driver finishes loading, so the tunnel is destroyed and never recreated. Kernel log (monotonic boot offsets): [ 4.97s] thunderbolt 0-1: new device found ... Dell Thunderbolt 4 Dock [ 17.72s] thunderbolt 0000:00:0d.2: 0:5 <-> 1:14 (DP): not active, tearing down [101.11s] xe 0000:00:02.0: [drm] Found pantherlake (device ID b080) integrated display [102.46s] [drm] Initialized xe 1.1.0 for 0000:00:02.0 The late xe load correlates with a stalled udev coldplug: `systemd- analyze blame` shows a cluster of device units (dev-rfkill, tpm0, ttyS0-3, ...) all settling at ~1min 39s, i.e. udev is wedged ~99s and only modprobes xe afterward. This ~99s stall does not occur on 7.0.0-15-generic. Recovery (confirms HW is fine): unplugging/replugging the single Thunderbolt cable AFTER boot (xe now loaded) immediately re- establishes the DP tunnel and DP-7 goes "connected" and the monitor lights up. The failure is purely the cold-boot ordering race. Hardware: - Dell XPS 16 (product_name "XPS 16 DA16260", board 0TVXV7), BIOS 1.5.1 (2026-04-01) - GPU: Intel Panther Lake [Arc B390] [8086:b080] (rev 04), driver: xe - Dock: Dell Thunderbolt 4 Dock (USB4, links at 40 Gb/s) -> DisplayPort -> external monitor - Session: Wayland (GNOME/mutter) Workarounds: replug the Thunderbolt cable after boot; or boot 7.0.0-15-generic. See also (same teardown signature, different distro/HW): https://github.com/basecamp/omarchy/issues/3906 ProblemType: Bug DistroRelease: Ubuntu 26.04 Package: linux-image-7.0.0-22-generic 7.0.0-22.22 ProcVersionSignature: Ubuntu 7.0.0-22.22-generic 7.0.0 Uname: Linux 7.0.0-22-generic x86_64 ApportVersion: 2.34.0-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: kgapos 6304 F.... pipewire kgapos 6325 F.... wireplumber /dev/snd/seq: kgapos 6304 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Wed Jun 3 20:48:43 2026 InstallationDate: Installed on 2026-05-28 (6 days ago) InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1) MachineType: Dell Inc. XPS 16 DA16260 ProcEnviron: LANG=en_US.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-ghostty XDG_RUNTIME_DIR=<set> ProcFB: 0 xedrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-22-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 StagingDrivers: intel_ipu7_isys intel_ipu7 UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 04/01/2026 dmi.bios.release: 1.5 dmi.bios.vendor: Dell Inc. dmi.bios.version: 1.5.1 dmi.board.name: 0TVXV7 dmi.board.vendor: Dell Inc. dmi.board.version: A02 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.ec.firmware.release: 1.2 dmi.modalias: dmi:bvnDellInc.:bvr1.5.1:bd04/01/2026:br1.5:efr1.2:svnDellInc.:pnXPS16DA16260:pvr:rvnDellInc.:rn0TVXV7:rvrA02:cvnDellInc.:ct10:cvr:sku0DBA:pfaDellLaptops: dmi.product.family: Dell Laptops dmi.product.name: XPS 16 DA16260 dmi.product.sku: 0DBA dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2155195/+subscriptions