Public bug reported:
Problem summary
===============
On an Acer Nitro AN17-41 laptop, Ubuntu 26.04 development branch with
kernel 6.19.0-9-generic fails to display video when the internal panel
and/or external USB-C display output are owned by the AMD iGPU.
This appears to be a regression or behavior change in the newer Linux graphics
stack, because the same machine and same monitor path work under:
- Windows 11
- Ubuntu 24.04.4 live ISO
The machine has:
- Acer Nitro AN17-41
- BIOS V1.25
- AMD Rembrandt / Radeon 680M iGPU (1002:1681)
- NVIDIA GeForce RTX 4050 Mobile / Max-Q dGPU (10de:28e1)
I collected logs over SSH from another device in the failing cases
because the machine was still alive even when both displays were black.
Observed behavior on Ubuntu 26.04 / kernel 6.19
================================================
When AMD owns the display outputs, the system boots but the displays
stay black.
This affects:
- the internal eDP panel
- an external monitor connected through the USB-C / DP output routed to Radeon
The logs repeatedly show amdgpu DC / DMUB failures such as:
- "Failed to enable ASSR"
- "No reply for DMUB command: status=3"
- "DMCUB error - collecting diagnostic data"
- "Error queueing DMUB command: status=2"
- "enabling link ... failed: 15"
In the failing cases, DRM can still detect AMD-owned outputs as
connected and enabled, but they remain black.
Environment
===========
OS:
- Ubuntu 26.04 (Resolute Raccoon development branch)
Kernel:
- 6.19.0-9-generic
Secure Boot:
- enabled
Hardware:
- Acer Nitro AN17-41
- BIOS V1.25
- AMD Radeon 680M iGPU
- NVIDIA RTX 4050 Mobile dGPU
Regression evidence
===================
I now have a working Linux control case on the same laptop and same
physical USB-C monitor path.
Tested with:
- Ubuntu 24.04.4 LTS live ISO
Results on Ubuntu 24.04.4:
1. Auto / hybrid mode:
- internal panel works
- external monitor connected to the Radeon-routed USB-C/DP output also works
2. NVIDIA GPU Only mode:
- internal panel works
- the same external monitor on the Radeon-routed USB-C/DP output also works
in my test
In both Ubuntu 24.04.4 test cases, the displays light up normally and I
do not see the repeated amdgpu DC/DMUB failure pattern that appears on
Ubuntu 26.04 / kernel 6.19.
This strongly suggests:
- the hardware is capable of driving both outputs under Linux
- the Radeon-routed USB-C output is not fundamentally broken on this laptop
- the issue is more likely a regression or missing quirk in the newer
graphics/kernel stack used in Ubuntu 26.04
Additional control evidence
===========================
The same USB-C monitor connected to the Radeon-routed USB-C output also
works in Windows 11 when switching to Extend mode with Win+P.
This further suggests that the physical hardware path is functional, and
that the failing configuration is specific to the newer Linux graphics
stack.
What works
==========
1. NVIDIA GPU Only mode in firmware / BIOS on Ubuntu 26.04:
- the internal laptop panel works
2. Windows 11:
- the USB-C monitor connected to the Radeon-routed USB-C output works in
Extend mode
3. Ubuntu 24.04.4 live ISO:
- Auto / hybrid mode works
- internal panel works
- Radeon-routed USB-C/DP external monitor works
- NVIDIA GPU Only mode also worked in my test, including the same USB-C
monitor
What does not work
==================
On Ubuntu 26.04 / kernel 6.19:
1. Hybrid / normal mode:
- if the internal panel is owned by AMD, the panel stays black
2. AMD-only test:
- booting with
module_blacklist=nvidia,nvidia_drm,nvidia_modeset,nvidia_uvm
- internal eDP stays black
- external USB-C/DP monitor routed to Radeon also stays black
This strongly suggests the issue is not caused by nvidia-drm handoff or
by both DRM stacks loading together.
How to reproduce
================
Case A: Hybrid / normal mode on Ubuntu 26.04
1. Boot Ubuntu 26.04 on Acer Nitro AN17-41.
2. Let the machine use its normal hybrid graphics routing.
3. If the internal panel is owned by AMD, the panel remains black.
Case B: AMD-only test on Ubuntu 26.04
1. Boot with:
module_blacklist=nvidia,nvidia_drm,nvidia_modeset,nvidia_uvm
2. Connect an external monitor to the USB-C / DP output routed to Radeon before
power-on.
3. Boot Ubuntu.
4. Result: both the internal panel and the external USB-C display remain black,
although the system is alive and reachable over SSH.
Case C: Verbose DRM logging on Ubuntu 26.04
1. Boot with:
drm.debug=0x1e log_buf_len=4M
module_blacklist=nvidia,nvidia_drm,nvidia_modeset,nvidia_uvm
2. Result: same black screens, with detailed DRM / amdgpu logging showing DMUB
/ ASSR / link enable failures.
Expected result
===============
When AMD owns the internal eDP panel and/or Radeon-routed USB-C/DP
output, the displays should light up normally and the system should
reach a visible graphical session.
Actual result
=============
The system boots, but the displays stay black. Logs indicate failures in
amdgpu DC / DMUB while trying to bring up AMD-owned display links.
Important log patterns
======================
Examples consistently seen in the affected Ubuntu 26.04 boots:
- "Skipping amdgpu DM backlight registration"
- "Failed to get EDID from ACPI: -19" (seen in verbose DRM logging)
- "boot timing validation failed ..."
- "Failed to enable ASSR"
- "No reply for DMUB command: status=3"
- "DMCUB error - collecting diagnostic data"
- "Error queueing DMUB command: status=2"
- "enabling link 0 failed: 15"
- "enabling link 2 failed: 15"
Why I think this is a kernel/amdgpu issue
=========================================
The issue reproduces when NVIDIA modules are blacklisted, so it does not
appear to depend on nvidia-drm being active.
The internal panel and the Radeon-routed external USB-C/DP output can
both be detected as connected/enabled by DRM, but they still remain
black.
The same hardware and same USB-C path work:
- on Windows 11
- on Ubuntu 24.04.4 live ISO
This makes it look like an amdgpu DC / DMUB / link bring-up failure in the
newer Ubuntu 26.04 graphics stack, rather than:
- a simple EDID-not-found case
- a generic Optimus/MUX problem
- a pure backlight-only issue
- a userspace / compositor-only issue
- a fundamental hardware limitation of the laptop
Tests already performed
=======================
On Ubuntu 26.04:
1. Normal hybrid boot
- black internal display when AMD owns it
2. NVIDIA GPU Only mode
- internal panel works
3. AMD-only boot with:
module_blacklist=nvidia,nvidia_drm,nvidia_modeset,nvidia_uvm
- both internal eDP and Radeon-routed USB-C/DP stayed black
4. Verbose DRM boot with:
drm.debug=0x1e log_buf_len=4M
- same failure, more detailed DMUB / ASSR / link logs
5. Test with:
amdgpu.sg_display=0
- no improvement
6. Test with:
amdgpu.abmlevel=0
- no improvement
On Ubuntu 24.04.4 live ISO:
7. Auto / hybrid mode
- internal panel works
- Radeon-routed USB-C/DP external monitor works
8. NVIDIA GPU Only mode
- internal panel works
- the same Radeon-routed USB-C/DP external monitor also worked in my test
Attachments
===========
I am attaching log bundles from these scenarios:
- gpu-badboot4-nvidiablacklist.zip
- gpu-badboot5-nvidiablacklistamdusbc.zip
- gpu-badboot6-nvidiablacklistamdusbcdbg.zip
- gpu-goodboot7-nvidiaonly-w-usbc-radeon.zip
- gpu-badboot8-sgzero.zip
- gpu-badboot9-abmzero.zip
- gpu-goodboot10-u24044.zip
- gpu-goodboot11-u24045.zip
These include:
- journalctl / dmesg output
- DRM connector status and enabled state
- lspci / module state
- backlight info
- EDID decode output
- verbose DRM logs where applicable
I can reproduce this reliably and I can collect additional logs over SSH
because the machine stays alive even when both displays are black.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-image-6.19.0-9-generic 6.19.0-9.9
ProcVersionSignature: Ubuntu 6.19.0-9.9-generic 6.19.5
Uname: Linux 6.19.0-9-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
AudioDevicesInUse:
USER PID ACCESS COMMAND
/dev/snd/controlC2: denixx 6079 F.... wireplumber
/dev/snd/controlC0: denixx 6079 F.... wireplumber
/dev/snd/controlC1: denixx 6079 F.... wireplumber
/dev/snd/seq: denixx 6059 F.... pipewire
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Mon Mar 16 08:26:28 2026
InstallationDate: Installed on 2026-03-15 (1 days ago)
InstallationMedia: Ubuntu 26.04 LTS "Resolute Raccoon" - Daily amd64 (20260313)
IwDevWlp4s0Link: Not connected.
MachineType: Acer Nitro AN17-41
ProcEnviron:
LANG=uk_UA.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
ProcFB:
0 amdgpudrmfb
1 nvidia-drmdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-6.19.0-9-generic
root=/dev/mapper/ubuntu--vg-ubuntu--lv ro quiet splash
crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/18/2024
dmi.bios.release: 1.25
dmi.bios.vendor: INSYDE Corp.
dmi.bios.version: V1.25
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Spacia_PEH
dmi.board.vendor: RB
dmi.board.version: V1.25
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: Chassis Version
dmi.ec.firmware.release: 1.11
dmi.modalias:
dmi:bvnINSYDECorp.:bvrV1.25:bd09/18/2024:br1.25:efr1.11:svnAcer:pnNitroAN17-41:pvrV1.25:rvnRB:rnSpacia_PEH:rvrV1.25:cvnAcer:ct10:cvrChassisVersion:sku0000000000000000:
dmi.product.family: Acer Nitro 17
dmi.product.name: Nitro AN17-41
dmi.product.sku: 0000000000000000
dmi.product.version: V1.25
dmi.sys.vendor: Acer
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute
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https://bugs.launchpad.net/bugs/2144530
Title:
Regression on Acer Nitro AN17-41: amdgpu DC/DMUB fails to light up
internal eDP and Radeon-routed USB-C/DP outputs on Ubuntu 26.04 /
kernel 6.19, while Ubuntu 24.04.4 live works
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