Public bug reported:
## Summary
Ubuntu 26.04 fails to power off my Dell XPS 8940 completely. The
operating system appears to finish its shutdown sequence, the display
turns black, and the storage devices spin down. However, the motherboard
remains powered, the internal fans continue operating, and the fans may
gradually increase in speed.
The same computer shuts down completely under Windows 11.
A custom GRUB menu entry containing the `halt` command also successfully
powers off the computer.
This suggests an issue in the Linux shutdown path or its interaction
with the Dell firmware. The underlying cause has not yet been
identified.
## Affected hardware
- Computer: Dell XPS 8940
- Processor: Intel Core i7-11700
- Memory: 32 GiB
- BIOS: Dell 2.27.1, dated April 3, 2025
- Integrated graphics: Intel UHD Graphics 750 (i915)
- Dedicated graphics: Intel Arc Pro B70, 32 GiB (Xe driver)
- Operating system: Ubuntu 26.04
- Primary tested kernel: 7.0.0-42-generic
- Additional tested kernel: 7.0.0-14-generic (Ubuntu live USB)
- Boot mode: UEFI
- Windows 11 is installed separately.
- Ubuntu 7.0.0-42.42-generic 7.0.14
The dedicated Intel Arc Pro B70 uses an external power supply. The
reported failure concerns the Dell motherboard and its internal fans
remaining powered. The effect of the external GPU power arrangement on
this issue has not been conclusively determined.
## Steps to reproduce
1. Boot Ubuntu normally.
2. Allow the operating system to finish starting.
3. Initiate a normal shutdown.
4. Observe that the display turns black and storage activity stops.
5. Observe that the Dell motherboard remains powered and the internal fans
continue running.
The system does not complete its physical power-off sequence.
## Expected result
The Dell XPS 8940 should power off completely, including the motherboard
power indicator and internal fans.
## Actual result
Ubuntu reaches the final stage of shutdown but does not power off the
computer completely.
The screen becomes black, storage activity stops, and the internal fans
continue operating.
A physical power-off intervention is required unless the GRUB workaround
is used.
## Tests performed
**Test 1 — Ubuntu 26.04, Linux 7.0.0-42**
Result: FAIL
Normal shutdown does not complete the physical power-off.
**Test 2 — Ubuntu 26.04 live USB, Linux 7.0.0-14**
Result: FAIL
The same shutdown failure occurs in the live environment.
This indicates that the problem is not limited to the installed Ubuntu
system or its user configuration.
**Test 3 — Ubuntu text-only environment**
Result: FAIL
Booting into `multi-user.target` without the normal graphical desktop
does not resolve the shutdown problem.
This makes GNOME an unlikely primary cause.
**Test 4 — Windows 11**
Result: PASS
A full Windows shutdown successfully powers off the same computer.
**Test 5 — GRUB power-off**
Result: PASS
I added this custom entry to `/etc/grub.d/40_custom`:
```grub
menuentry "Power Off via GRUB" {
halt
}
```
After running `sudo update-grub`, rebooting into GRUB, and selecting
this entry, the Dell XPS 8940 powers off completely.
This workaround has been verified on the affected computer.
## Additional observations
- The issue appeared around the transition to Ubuntu's Linux 7.0 kernels.
- The system previously experienced intermittent freezes, but their
relationship to the shutdown failure has not been established.
- A separate Intel Xe GPU engine fault was recorded during an earlier session.
Its relationship to the shutdown failure is unknown.
- System logs show that systemd reaches its shutdown services, but the
available logs do not identify the precise point at which the final hardware
power-off fails.
- Boot logs contain ACPI firmware warnings. Their relevance to the shutdown
failure remains unproven.
The current kernel command line also contains:
`xe.force_probe=* pcie_aspm=off pcie_port_pm=off reboot=pci`
The effect of these parameters on this shutdown problem has not been
isolated.
## Similar independent report
A separate Dell XPS 8940 user reported substantially similar symptoms
under Manjaro Linux with kernel 6.19.2.
That computer used an AMD Radeon GPU rather than an Intel Arc Pro B70.
The user also confirmed that GRUB's `halt` command successfully powered
off the computer.
This suggests that the problem may not be exclusive to Ubuntu, Linux
7.0, or Intel Xe graphics. However, the reports have not been
demonstrated to share the same root cause.
Manjaro forum discussion: "New Install Shutdown Turns Off Monitor But
Power LED & Fans Still Run" (March 2026).
## Workaround documentation
I have published the tested GRUB workaround, troubleshooting results,
and optional shutdown scripts in this public repository:
github.com/MikeCaldera/dell-xps8940-linux-grub-poweroff
## Request
Please investigate whether this is a Linux kernel power-management,
ACPI, UEFI, or Dell firmware interaction affecting the XPS 8940.
The GRUB `halt` workaround confirms that the computer can power off
through an alternative boot-environment path.
I am willing to provide additional diagnostic information and perform
non-destructive tests to help isolate the cause.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "Reduced PCI hardware inventory (lspci -nn). Reviewed for
sensitive information. Detailed diagnostics withheld pending privacy review."
https://bugs.launchpad.net/bugs/2172556/+attachment/6013554/+files/lspci-nn-review.log
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https://bugs.launchpad.net/bugs/2172556
Title:
Dell XPS 8940 fails to power off completely on Ubuntu 26.04 Linux 7.0
kernels; GRUB halt succeeds
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