After today’s update to kernel 6.8.0-59 (and the corresponding Xwayland/Mutter upgrades), the HDMI monitor is no longer detected when the Thunderbolt (DP‑ALT) dock is connected.
On kernel 6.8.0-57 with the previous graphics stack, the internal display, HDMI output, and docked monitor all worked together correctly. ** Description changed: On Ubuntu 24.04 LST with the stock kernel 6.8.0‑59‑generic, when I connect two external monitors—one via the laptop’s HDMI port and one via a Lenovo Thunderbolt dock (DP‑ALT pass‑through)—the HDMI‑connected monitor is no longer detected (it vanishes from xrandr). If I unplug the dock, the HDMI monitor returns; even if I boot an older kernel (6.8.0‑57), both monitors don't work simultaneously. Expected behavior: Both external monitors (HDMI‑2 and DP‑6), and the internal eDP‑1, should be detected and driven simultaneously. Actual behavior: Only eDP‑1 (internal) + DP‑6 (dock) are active; HDMI‑2 is not even listed by xrandr. Hardware: - Laptop: Lenovo T480s + Laptop: Lenovo T480s - Dock: Lenovo Thunderbolt Dock (DP‑ALT, no MST) + Dock: Lenovo Thunderbolt Dock (DP‑ALT, no MST) - Monitors: + Monitors: - eDP‑1 (internal) 1920×1080 + eDP‑1 (internal) 1920×1080 - HDMI‑2 2560×1440 (direct) + HDMI‑2 2560×1440 (direct) - DP‑6 2560×1440 (via dock) + DP‑6 2560×1440 (via dock) Steps to reproduce: - Boot into kernel 6.8.0‑59‑generic. + Boot into kernel 6.8.0‑59‑generic. - Log in to Ubuntu on Wayland or Xorg. + Log in to Ubuntu on Wayland or Xorg. - Connect one monitor to the laptop HDMI port. + Connect one monitor to the laptop HDMI port. - Connect a second monitor to the Thunderbolt dock. + Connect a second monitor to the Thunderbolt dock. - Run: xrandr + Run: xrandr Observe that DP-6 is “connected” but HDMI-2 is missing. ProblemType: Bug DistroRelease: Ubuntu 24.04 Package: linux-image-6.8.0-59-generic 6.8.0-59.61 ProcVersionSignature: Ubuntu 6.8.0-59.61-generic 6.8.12 Uname: Linux 6.8.0-59-generic x86_64 ApportVersion: 2.28.1-0ubuntu3.5 Architecture: amd64 AudioDevicesInUse: - USER PID ACCESS COMMAND - /dev/snd/seq: lorenzo 3504 F.... pipewire - /dev/snd/controlC0: lorenzo 3508 F.... wireplumber - /dev/snd/controlC1: lorenzo 3508 F.... wireplumber + USER PID ACCESS COMMAND + /dev/snd/seq: lorenzo 3504 F.... pipewire + /dev/snd/controlC0: lorenzo 3508 F.... wireplumber + /dev/snd/controlC1: lorenzo 3508 F.... wireplumber CasperMD5CheckResult: unknown CurrentDesktop: ubuntu:GNOME Date: Fri May 2 21:31:15 2025 InstallationDate: Installed on 2023-04-26 (737 days ago) InstallationMedia: Ubuntu 23.04 "Lunar Lobster" - Release amd64 (20230418) MachineType: LENOVO 20L8S8K30L ProcFB: 0 i915drmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-59-generic root=UUID=a4811af7-d5ef-4599-ba77-d723e024b360 ro quiet splash vt.handoff=7 RelatedPackageVersions: - linux-restricted-modules-6.8.0-59-generic N/A - linux-backports-modules-6.8.0-59-generic N/A - linux-firmware 20240318.git3b128b60-0ubuntu2.11 + linux-restricted-modules-6.8.0-59-generic N/A + linux-backports-modules-6.8.0-59-generic N/A + linux-firmware 20240318.git3b128b60-0ubuntu2.11 SourcePackage: linux UpgradeStatus: Upgraded to noble on 2024-08-27 (248 days ago) dmi.bios.date: 03/17/2025 dmi.bios.release: 1.60 dmi.bios.vendor: LENOVO dmi.bios.version: N22ET83W (1.60 ) dmi.board.asset.tag: Not Available dmi.board.name: 20L8S8K30L dmi.board.vendor: LENOVO dmi.board.version: SDK0J40697 WIN dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: None dmi.ec.firmware.release: 1.23 dmi.modalias: dmi:bvnLENOVO:bvrN22ET83W(1.60):bd03/17/2025:br1.60:efr1.23:svnLENOVO:pn20L8S8K30L:pvrThinkPadT480s:rvnLENOVO:rn20L8S8K30L:rvrSDK0J40697WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20L8_BU_Think_FM_ThinkPadT480s: dmi.product.family: ThinkPad T480s dmi.product.name: 20L8S8K30L dmi.product.sku: LENOVO_MT_20L8_BU_Think_FM_ThinkPad T480s dmi.product.version: ThinkPad T480s dmi.sys.vendor: LENOVO -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2109863 Title: Regression: HDMI output not detected when Thunderbolt (DP‑ALT) dock is connected on kernel 6.8.0‑59 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2109863/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
