[amdgpu] since Linux kernel 6.5.0-14 external monitors are no longer detected

[Roel Harbers]

on my Lenovo ThinkPad P14s gen 4, external monitors are no longer detected since installing 6.5.0-14.

Neither USB-C nor HDMI work. hwinfo and the "Displays" util don't show any additional monitors, only the built-in one.

Charging through the monitor does work. also, the built-in USB hub of the monitor works.

I have tried with 2 external monitors (both ultra-wide, one Dell, one Samsung)

Going back to 6.5.0-13 fixes everything.

Let me know if there's any way I can help troubleshoot this.

ProblemType: Bug
DistroRelease: Ubuntu 23.10
Package: linux-image-6.5.0-14-generic 6.5.0-14.14
ProcVersionSignature: Ubuntu 6.5.0-14.14-generic 6.5.3
Uname: Linux 6.5.0-14-generic x86_64
ApportVersion: 2.27.0-0ubuntu5
Architecture: amd64
CRDA: N/A
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Jan 19 17:17:54 2024
InstallationDate: Installed on 2023-11-16 (64 days ago)
InstallationMedia: Ubuntu 23.10.1 "Mantic Minotaur" - Release amd64 (20231016.1)
MachineType: {report['dmi.sys.vendor']} {report['dmi.product.name']}
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.5.0-14-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-6.5.0-14-generic N/A
 linux-backports-modules-6.5.0-14-generic N/A
 linux-firmware 20230919.git3672ccab-0ubuntu2.5
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/24/2023
dmi.bios.release: 1.16
dmi.bios.vendor: LENOVO
dmi.bios.version: R2FET36W (1.16 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21K5CTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.11
dmi.modalias: dmi:bvnLENOVO:bvrR2FET36W(1.16):bd10/24/2023:br1.16:efr1.11:svnLENOVO:pn21K5CTO1WW:pvrThinkPadP14sGen4:rvnLENOVO:rn21K5CTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21K5_BU_Think_FM_ThinkPadP14sGen4:
dmi.product.family: ThinkPad P14s Gen 4
dmi.product.name: 21K5CTO1WW
dmi.product.sku: LENOVO_MT_21K5_BU_Think_FM_ThinkPad P14s Gen 4
dmi.product.version: ThinkPad P14s Gen 4
dmi.sys.vendor: LENOVO

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Roel Harbers (comavn)]

Also affects 6.5.0-15

I just noticed that on reboot, a text-mode error message flashes past:

systemd-shutdown[1]: Could not detach DM /dev/dm-0: Device or res [truncated]
systemd-shutdown[1]: Failed to finalize DM devices, ignoring.

6.5.0.13 doesn't do that. No idea if it's related or not.

[Roel Harbers (comavn)]

I just "fixed" this: turns out, I have, at some point in the past, added `blacklist amdgpu` to `/etc/modprobe.d`, as part of an unrelated troubleshooting session probably, and forgot about it.

I don't know why that wouldn't break 6.5.0-13 as well; maybe `update-initramfs` failed or wasn't executed so the config didn't get into the initramfs image.

Anyway, I removed the blacklist line and ran `update-initramfs`, after which everything works fine.

Sorry for the distraction.