Public bug reported:
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
Dock: Lenovo Thunderbolt Dock (DP‑ALT, no MST)
Monitors:
eDP‑1 (internal) 1920×1080
HDMI‑2 2560×1440 (direct)
DP‑6 2560×1440 (via dock)
Steps to reproduce:
Boot into kernel 6.8.0‑59‑generic.
Log in to Ubuntu on Wayland or Xorg.
Connect one monitor to the laptop HDMI port.
Connect a second monitor to the Thunderbolt dock.
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
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
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
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
** Attachment added: "version.log"
https://bugs.launchpad.net/bugs/2109863/+attachment/5875457/+files/version.log
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in 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
Status in linux package in Ubuntu:
New
Bug description:
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
Dock: Lenovo Thunderbolt Dock (DP‑ALT, no MST)
Monitors:
eDP‑1 (internal) 1920×1080
HDMI‑2 2560×1440 (direct)
DP‑6 2560×1440 (via dock)
Steps to reproduce:
Boot into kernel 6.8.0‑59‑generic.
Log in to Ubuntu on Wayland or Xorg.
Connect one monitor to the laptop HDMI port.
Connect a second monitor to the Thunderbolt dock.
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
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
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
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