Bug 505554

SUMMARY
Typically while idling at the desktop with no programs opened by the user, my laptop (AMD 7840U with 780M) will report 3-4w usage by the SOC. I can connect to a USB-C dock with external monitor, and nothing will change. In this state, GPU fully downclocks, CPU and GPU utilization reported for plasmashell both sit at 0% (aside from intermittent spikes), and CPU for kwin_wayland averages 0% as well.

However, if I then disconnect from the USB-C dock after having been connected, reported SOC power usage will jump to 8-9w, radeontop reports the GPU does not clock down, SOC temperatures rise and fans ramp. When I looked for the cause, I noticed plasmashell will sit at reported 11-15% GPU utilization and around 10% CPU utilization, while kwin_wayland jumps between 5% and 50% CPU utilization, as reported by top.

This load will continue indefinitely until I:

a) reconnect to USB dock
b) restart kwin_wayland (systemctl --user restart plasma-kwin_wayland.service)
c) reboot the laptop

Once I take any of the 3 above actions, CPU usage by kwin_wayland and both CPU and GPU usage by plasmashell will drop to 0% again while system is idle, and power and clocks drop accordingly. However, if the way I resolve is to restart kwin_wayland, the usage will come back if I plug something other than the dock into the USB port. Rebooting the laptop and reconnecting to dock resolve indefinitely (at least until the next time I connect to and disconnect from the dock).

STEPS TO REPRODUCE
1. Connect to a USB-C dock which has external monitor attached (via HDMI)
2. Disconnect from the dock

OBSERVED RESULT
System idle power consumption jumps by 5w, constant low GPU and CPU load by plasmashell and CPU load by kwin_wayland, even while system is doing nothing.

EXPECTED RESULT
System will idle at same power and clocks as it did before and while it was connected to the dock, no/low compute consumption by kwin_wayland and plasmashell while at idle.

SOFTWARE/OS VERSIONS
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: Fedora Linux 42
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.1

ADDITIONAL INFORMATION

Example outputs before unplug:

lm sensors:
sensors amdgpu-pci-c100 cros_ec-isa-0000
amdgpu-pci-c100
Adapter: PCI adapter
vddgfx:      856.00 mV
vddnb:       856.00 mV
edge:         +37.0°C
PPT:           8.04 W  (avg =   4.13 W)

cros_ec-isa-0000
Adapter: ISA adapter
fan1:               0 RPM
local_f75303@4d:  +26.9°C
cpu_f75303@4d:    +28.9°C
ddr_f75303@4d:    +26.9°C
cpu@4c:           +39.9°C

# from nvtop
 GPU[                             0%] MEM[|||||||||       0.608Gi/2.000Gi]
 GPU 800MHz  MEM 1600MHz TEMP  34°C   CPU-FAN   POW   4 W

    PID USER DEV     TYPE  GPU        GPU MEM    CPU  HOST MEM Command
   3030 user   0 Both G+C   0%    250MiB  12%     0%    523MiB /usr/bin/plasmashell --no-respawn

After disconnecting from dock (continues indefinitely until action is taken):

lm sensors:
sensors amdgpu-pci-c100 cros_ec-isa-0000
amdgpu-pci-c100
Adapter: PCI adapter
vddgfx:      849.00 mV
vddnb:       940.00 mV
edge:         +44.0°C
PPT:           9.24 W  (avg =   8.17 W)

cros_ec-isa-0000
Adapter: ISA adapter
fan1:            2693 RPM
local_f75303@4d:  +43.9°C
cpu_f75303@4d:    +41.9°C
ddr_f75303@4d:    +41.9°C
cpu@4c:           +45.9°C

#nvtop
    PID USER DEV     TYPE  GPU        GPU MEM    CPU  HOST MEM Command
   2973 user   0 Both G+C  13%    277MiB  14%     8%    536MiB /usr/bin/plasmashell --no-respawn

#top
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   2718 user      -2   0 2737916 311212 226292 S   8.3   0.3   3:09.24 kwin_wayland
   2973 user      20   0   10.0g 549748 215192 S   7.3   0.6   0:46.07 plasmashell