https://bugs.kde.org/show_bug.cgi?id=522172
Bug ID: 522172
Summary: Spurious reboot / hang on shutdown after Plasma 6.7
update due to unmasked USB ACPI wake states
(XHC0/PTXH)
Classification: Plasma
Product: plasmashell
Version First 6.7.0
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Power management & brightness
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: 1.0
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DESCRIPTION
Since I updated a few days ago from 6.6 to 6.7 - I have the issue that it does
reboot instead of shutdown.
Since I’m a total noob even after 2 years being on Arch (Linux in general), I
let AI write the report lol - hope it helps anyways:
Description of the Issue:
Following a recent system upgrade to KDE Plasma 6.7, the system fails to
complete a standard hardware power-off sequence. Systemd completes userspace
teardown and unmounts all local filesystems cleanly, closing the journal log
successfully.
However, at the physical handoff state, the machine either hangs indefinitely
at the terminal prompt or immediately executes an unexpected hardware reboot
instead of shutting down. Bypassing systemd via raw kernel SysRq injection
(echo o > /proc/sysrq-trigger) results in an immediate, clean power down,
isolating the issue to a hardware-state handoff negotiation.
Root Cause Analysis:
The updated desktop compositor configuration leaves trailing state-polling
signals on the main system buses right at the millisecond of power termination.
The motherboard firmware incorrectly interprets this residual power fluctuation
on the energized AMD and ASMedia USB host controller interfaces (XHC0 and PTXH)
as an ACPI wake event. This forces the hardware into an immediate safety reset
or lock state.
Steps to Reproduce:
- Boot into the desktop session.
- Trigger a normal system shutdown via the UI session menu.
- Observe the system fail to cut power to the motherboard rails.
Resolution / Workaround:
The issue is fully resolved by masking the responsible USB hardware controllers
from the kernel ACPI wakeup register before initiating shutdown.
Toggling the state of the controllers in /proc/proc/acpi/wakeup:
echo “XHC0” > /proc/acpi/wakeup
echo “PTXH” > /proc/acpi/wakeup
Disabling these wake targets allows the system to drop power rails cleanly and
permanently on every subsequent shutdown command.
SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.7.0
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
Kernel Version: 7.0.12-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5700X3D 8-Core Processor
Memory: 32 GiB of RAM (31.3 GiB usable)
Graphics Processor: AMD Radeon RX 9070 XT
Mainboard Hardware: MSI B450 GAMING PLUS MAX (MS-7B86)
Mainboard Firmware Version: UEFI AMI H.N0 (03/21/2025)
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