looks like this report isnt accurate...
up to the time i posted, it appears simply a coincidence that the fans stopped running within 30 seconds of killall pipewire (fan running constantly for 10minutes+ upto that point). it did seem to be the cause - 4-5 times i tested the theory before posting.
fyi, the issue currently looks like its something to do with fedora power management. Laptop works out of the box with ubuntu, but fedora needed a number of the 'Tunables' enabled in Powertop to get the same battery life.
recently I got a new laptop and installed Fedora34 (didnt seem to matter if KDE or Gnome). I immediately noticed CPU fans would run constantly (95%+ duty cycle). Being unfamiliar with the laptop, I tried Ubuntu 20.10/21.04 and noticed the fans are typically off (5% duty cycle).
I've now installed Fedora35 (KDE, rawhide) to look into the issue again and the constantly running fan is back.
After some diagnosing, it appears to be something about 'pipewire' process. It appears that when the fans come on and pipewire process is running, the fans will not turn off.
If i 'killall -9 pipewire' then within moments, the fans will turn off and fans then appear to act normally.
just noticed i haven't included top. CPU time is fully idle (0-5% load at most) so it's not a bad process.
as i'm sure you're aware, after killall then pw-top will close. if i rerun it, then pipewire process will return.
as per screenshots of before & after killall; i've included pw-top, lm-sensors filtered to fan rpm, dmesg of audio hardware (incase it's an audio issue), and powertop.
Laptop is Dell XPS13 9305, i5 1135G7, intel Xe iGPU. What i have just noticed is that the laptop feels slightly warmer around the 'RTY' area of the keyboard. the 9305 appears to be based upon the 2019 XPS13 layout (https://laptopmedia.com/gb/comparisons/comparison-dell-xps-13-9300-2020-vs-dell-xps-13-7390-2019-whats-changed/) so looks like it could well be CPU/gpu related.
edit: gpu info could possible be useful:
$ glxinfo -B
name of display: :1
display: :1 screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
Vendor: Intel (0x8086)
Device: Mesa Intel(R) Xe Graphics (TGL GT2) (0x9a49)
Version: 21.1.2
Accelerated: yes
Video memory: 3072MB
Unified memory: yes
Preferred profile: core (0x1)
Max core profile version: 4.6
Max compat profile version: 4.6
Max GLES1 profile version: 1.1
Max GLES[23] profile version: 3.2
OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) Xe Graphics (TGL GT2)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 21.1.2
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL version string: 4.6 (Compatibility Profile) Mesa 21.1.2
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 21.1.2
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
no idea what it is - i figured it was normal behaviour. Quick search shows it's Plasma PulseAudio (https://archlinux.org/packages/extra/x86_64/plasma-pa/). I guess Fedora/KDE uses the same tool.
both speakers & mic are muted, and there's no applications playing audio according to the volume icon in taskbar.
bit more system info: pipewire highest consumer in htop (<5%), but not much else showing in the other output windows.
recently I got a new laptop and installed Fedora34 (didnt seem to matter if KDE or Gnome). I immediately noticed CPU fans would run constantly (95%+ duty cycle). Being unfamiliar with the laptop, I tried Ubuntu 20.10/21.04 and noticed the fans are typically off (5% duty cycle).
I've now installed Fedora35 (KDE, rawhide) to look into the issue again and the constantly running fan is back.
After some diagnosing, it appears to be something about 'pipewire' process. It appears that when the fans come on and pipewire process is running, the fans will not turn off.
If i 'killall -9 pipewire' then within moments, the fans will turn off and fans then appear to act normally.
just noticed i haven't included top. CPU time is fully idle (0-5% load at most) so it's not a bad process.
as i'm sure you're aware, after killall then pw-top will close. if i rerun it, then pipewire process will return.
as per screenshots of before & after killall; i've included pw-top, lm-sensors filtered to fan rpm, dmesg of audio hardware (incase it's an audio issue), and powertop.
Laptop is Dell XPS13 9305, i5 1135G7, intel Xe iGPU. What i have just noticed is that the laptop feels slightly warmer around the 'RTY' area of the keyboard. the 9305 appears to be based upon the 2019 XPS13 layout (https://laptopmedia.com/gb/comparisons/comparison-dell-xps-13-9300-2020-vs-dell-xps-13-7390-2019-whats-changed/) so looks like it could well be CPU/gpu related.
edit: gpu info could possible be useful:
$ glxinfo -B
name of display: :1
display: :1 screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
Vendor: Intel (0x8086)
Device: Mesa Intel(R) Xe Graphics (TGL GT2) (0x9a49)
Version: 21.1.2
Accelerated: yes
Video memory: 3072MB
Unified memory: yes
Preferred profile: core (0x1)
Max core profile version: 4.6
Max compat profile version: 4.6
Max GLES1 profile version: 1.1
Max GLES[23] profile version: 3.2
OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) Xe Graphics (TGL GT2)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 21.1.2
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL version string: 4.6 (Compatibility Profile) Mesa 21.1.2
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 21.1.2
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20