Public bug reported:
Summary
System hangs during boot on Lenovo ThinkPad P16s Gen 4 AMD when no HDMI display
is connected. The hang occurs during AMD GPU display
connector detection.
System Information
Hardware
Model: Lenovo ThinkPad P16s Gen 4 AMD
Model Number: 21RX0013MH
GPU: AMD Radeon 890M (Device ID: 1002:150E)
CPU: AMD Ryzen AI 9 HX PRO 370
BIOS: R2XET35W (1.15) - Released 08/29/2025
Software
OS: Ubuntu 24.04 (Noble)
Kernel: 6.14.0-36-generic
Distro: Ubuntu
Problem Description
Symptoms
System hangs during boot when no HDMI cable is connected
Hang occurs during AMD GPU initialization/connector detection phase
System boots successfully with HDMI cable connected
System boots successfully with nomodeset kernel parameter (but disables
graphics acceleration)
Boot Log Location
The system hangs after these messages: [drm] initializing kernel modesetting
(IP DISCOVERY 0x1002:0x150E 0x17AA:0x512F
0x01) amdgpu: Fetched VBIOS from VFCT amdgpu: ATON BIOS: 113-STRIXEMU-001
amdgpu: VPE: collaborate mode false
amdgpu: [drm] Optional firmware "amdgpu/isp_4_1_0.bin" was not found
After this point, the system hangs indefinitely.
Workarounds
Connect HDMI cable during boot (system boots normally)
Add nomodeset to GRUB kernel command line (disables KMS/graphics acceleration)
Custom kernel with connector detection skip parameter (workaround patch)
Technical Details
Root Cause Analysis
The hang occurs in the DRM connector detection code path: - Function:
drm_helper_probe_detect() → amdgpu_dm_connector_detect() -
Location: drivers/gpu/drm/drm_probe_helper.c and
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c - Issue: Connector
detection blocks indefinitely when no display is connected on Device 150e
Affected Components
DRM: drivers/gpu/drm/drm_probe_helper.c
AMDGPU: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
Hardware: AMD Device 1002:150E (Radeon 890M)
Steps to Reproduce
Boot Lenovo ThinkPad P16s Gen 4 AMD system
Ensure no HDMI/DisplayPort cable is connected
Boot normally (without nomodeset)
System hangs during GPU initializationExpected Behavior
System should boot successfully even when no displays are connected. Connector
detection should either: - Complete quickly and report no
displays connected - Timeout gracefully after a reasonable delay - Defer
detection until after boot completes
Current Workaround
A workaround patch has been created that adds a kernel parameter to skip
connector detection: - Parameter:
skip_connector_detection_boot=1 - Location: Applied to
drivers/gpu/drm/drm_probe_helper.c
Request
Please investigate and fix the connector detection hang for AMD Device 150e
when no displays are connected during boot. The fix should allow
the system to boot successfully without requiring nomodeset or workarounds.
Additional Information
This appears to be specific to Device 150e (Radeon 890M)
Similar issues may affect other recent AMD GPUs
Firmware (BIOS) is up-to-date according to fwupd
Issue persists across kernel versions 6.14.x
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: linux-image-6.14.0-36-generic 6.14.0-36.36~24.04.1
ProcVersionSignature: Ubuntu 6.14.0-36.36~24.04.1-generic 6.14.11
Uname: Linux 6.14.0-36-generic x86_64
ApportVersion: 2.28.1-0ubuntu3.8
Architecture: amd64
CRDA: N/A
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Mon Dec 1 11:17:32 2025
InstallationDate: Installed on 2025-09-24 (68 days ago)
InstallationMedia: Kubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
MachineType: LENOVO 21RX0013MH
ProcFB: 0 simpledrmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.14.0-36-generic
root=UUID=3226c98c-7705-47aa-9996-394fd04c62f9 ro
resume=UUID=e8d43665-81c3-4471-873f-21c9cdb815b8 amdgpu.backlight=1
amdgpu.gpu_recovery=1 acpi_osi=Linux drm.vblankoffdelay=1
mem_sleep_default=s2idle amdgpu.dc=0 nomodeset
RelatedPackageVersions:
linux-restricted-modules-6.14.0-36-generic N/A
linux-backports-modules-6.14.0-36-generic N/A
linux-firmware 20240318.git3b128b60-0ubuntu2.21
SourcePackage: linux-hwe-6.14
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/29/2025
dmi.bios.release: 1.15
dmi.bios.vendor: LENOVO
dmi.bios.version: R2XET35W (1.15 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21RX0013MH
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: 1.8
dmi.modalias:
dmi:bvnLENOVO:bvrR2XET35W(1.15):bd08/29/2025:br1.15:efr1.8:svnLENOVO:pn21RX0013MH:pvrThinkPadP16sGen4AMD:rvnLENOVO:rn21RX0013MH:rvrSDK0T76576WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21RX_BU_Think_FM_ThinkPadP16sGen4AMD:
dmi.product.family: ThinkPad P16s Gen 4 AMD
dmi.product.name: 21RX0013MH
dmi.product.sku: LENOVO_MT_21RX_BU_Think_FM_ThinkPad P16s Gen 4 AMD
dmi.product.version: ThinkPad P16s Gen 4 AMD
dmi.sys.vendor: LENOVO
** Affects: ubuntu
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
** Attachment added: "KERNEL_BUG_REPORT.md"
https://bugs.launchpad.net/bugs/2133495/+attachment/5930636/+files/KERNEL_BUG_REPORT.md
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https://bugs.launchpad.net/bugs/2133495
Title:
Ubuntu can't boot up without nomodeset on amd
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