Public bug reported:
System Information:
Hardware: Lenovo ThinkPad T14s Gen 6 (Model: 21M1000MMX)
CPU/GPU: AMD Ryzen AI 7 PRO 360 with Radeon 880M (DCN 3.5)
$ lsb_release -rd
No LSB modules are available.
Description: Ubuntu 24.04.4 LTS
Release: 24.04
$ apt-cache policy linux-oem-6.17
linux-oem-6.17:
Installed: (none)
Candidate: 6.17.0-1017.17
Version table:
6.17.0-1017.17 500
500 http://archive.ubuntu.com/ubuntu noble-updates/main amd64 Packages
500 http://security.ubuntu.com/ubuntu noble-security/main amd64 Packages
Kernel: 6.17.0-1017-oem
Description:
When attempting to use 4 simultaneous displays (1x Internal eDP, 1x external
USB-C (2x monitors chained), 1x external HDMI monitor), the HDMI port fails to
output a signal upon hotplugging or waking from suspend.
The hardware is fully capable of driving all 4 displays, as a cold boot
with all cables attached works perfectly. However, on hotplug or wake,
the amdgpu driver appears to suffer from a state-tracking bug where it
fails to properly release a CRTC or MST bandwidth payload.
During the failure state, xrandr reports that the HDMI output is
connected and active with a valid resolution, but the physical monitor
receives no signal (black screen).
Steps to Reproduce:
Boot the system with 1x internal eDP and 2x USB-C monitors active.
Hotplug an HDMI monitor.
The HDMI monitor is detected by the OS but remains physically black.
Expected Behavior:
The HDMI monitor should light up immediately, utilizing the 4th available
display pipe on the Radeon 880M.
Actual Behavior:
The HDMI monitor stays black. The GPU acts as if it is out of resources,
despite xrandr showing the display as active.
Debugging / Workarounds Discovered:
The TTY Shuffle (SUCCESS): Pressing Ctrl+Alt+F3 to drop to a tty,
followed immediately by Ctrl+Alt+F2 to return to Wayland, forces the
driver to rebuild the display tree. The HDMI monitor wakes up after 2
seconds alongside the other 3 screens after CTRL+Alt+F3.
Hardware eDP Disable (SUCCESS): Closing the laptop lid (triggering an
ACPI hardware interrupt) forcefully kills the eDP pipe, which instantly
allows the HDMI port to light up.
Software eDP Disable (FAIL): Using GNOME Settings to toggle the Built-in
Display to "Off" does not wake up the HDMI port, indicating the driver
still holds the pipe/bandwidth hostage when disabled via software.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.17.0-1017-oem 6.17.0-1017.17
ProcVersionSignature: Ubuntu 6.17.0-1017.17-oem 6.17.13
Uname: Linux 6.17.0-1017-oem x86_64
NonfreeKernelModules: zfs
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Tue Apr 7 13:02:45 2026
HibernationDevice: RESUME=/dev/mapper/dm_crypt-0
InstallationDate: Installed on 2026-03-23 (15 days ago)
InstallationMedia: Ubuntu 24.04.4 LTS "Noble Numbat" - Release amd64 (20260210)
MachineType: LENOVO 21M1000MMX
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/BOOT/ubuntu_q06wtv@/vmlinuz-6.17.0-1017-oem
root=ZFS=rpool/ROOT/ubuntu_q06wtv ro quiet splash amdgpu.vramlimit=4096
amdgpu.sg_display=0 amdgpu.dcfeaturemask=0xA ttm.pages_limit=4194304
amdttm.pages_limit=4194304 resume=/dev/mapper/dm_crypt-0 vt.handoff=1
RelatedPackageVersions:
linux-restricted-modules-6.17.0-1017-oem N/A
linux-backports-modules-6.17.0-1017-oem N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.25
SourcePackage: linux-oem-6.17
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/10/2025
dmi.bios.release: 1.16
dmi.bios.vendor: LENOVO
dmi.bios.version: R2NET42W (1.16 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21M1000MMX
dmi.board.vendor: LENOVO
dmi.board.version: SDK0T76576 WIN
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.10
dmi.modalias:
dmi:bvnLENOVO:bvrR2NET42W(1.16):bd10/10/2025:br1.16:efr1.10:svnLENOVO:pn21M1000MMX:pvrThinkPadT14sGen6:rvnLENOVO:rn21M1000MMX:rvrSDK0T76576WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21M1_BU_Think_FM_ThinkPadT14sGen6:
dmi.product.family: ThinkPad T14s Gen 6
dmi.product.name: 21M1000MMX
dmi.product.sku: LENOVO_MT_21M1_BU_Think_FM_ThinkPad T14s Gen 6
dmi.product.version: ThinkPad T14s Gen 6
dmi.sys.vendor: LENOVO
** Affects: linux-oem-6.17 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble wayland-session
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https://bugs.launchpad.net/bugs/2147437
Title:
HDMI hotplug black screen on Ryzen AI 7 with 1x USB-C (2 screens dock)
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