Public bug reported:
Since upgrading from Ubuntu 24.04 to 26.04, the external HDMI monitor no
longer receives a signal after the session has been locked (Super+L or
idle timeout) and unlocked again. This did not happen on 24.04 with the
same hardware.
Steps to reproduce:
1. Laptop with external monitor connected via HDMI (output HDMI-A-1 on the
Intel GPU), Wayland session.
2. Lock the screen (Super+L) and wait until the external monitor goes into
standby.
3. Unlock with the password.
Expected: the external monitor shows the desktop again.
Actual: the internal panel works, but the external monitor reports "no signal
on HDMI 1". GNOME still treats the monitor as connected and active.
Observations while in the failed state:
- Kernel connector card1-HDMI-A-1 reports status=connected, enabled=enabled,
dpms=On.
- The kernel log shows i915_hotplug_work_func running at unlock time, with no
i915 errors (no link training or EDID errors).
- gnome-shell logs "Unexpected non-NULL onscreen_native->next_frame" around the
unlock.
- Changing the refresh rate of the external monitor in Settings > Displays
(forcing a new modeset) immediately restores the picture. Unplugging and
replugging the HDMI cable also restores it.
Hardware:
- HP ZBook Power 15.6 inch G8 Mobile Workstation PC
- Intel TigerLake-H GT1 UHD Graphics (i915) + NVIDIA RTX A2000 Mobile (nvidia
580); the HDMI port is wired to the Intel GPU
- External monitor: Dell U3423WE, 3440x1440
Software: Ubuntu 26.04.1 LTS, kernel 7.0.0-38-generic, mutter
50.1-0ubuntu2.4, gnome-shell 50.1-0ubuntu1.3, Wayland session.
Possibly related: bug #1968040. However, the "drmModeAtomicCommit:
Invalid argument" error from that bug does not appear in my logs.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: mutter (not installed)
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Thu Oct 8 07:34:45 2026
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/usr/bin/zsh
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: mutter
UpgradeStatus: Upgraded to resolute on 2026-09-29 (9 days ago)
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2169932
Title:
[i915] External HDMI monitor gets no signal after lock/unlock on 26.04
(regression from24.04)
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