Created attachment 278463 [details]
alsa-info.sh output and strace of i8kctl
Running i8kctl fan causes an audio shutter/click.
I encountered the issue while running i8kmon with a timer of 2 seconds. It caused an audible "click" every 2 seconds on the audio stream.
The issue manifested itself only with an external USB audio card (focusrite scarlet 2i2) and did not manifest itself with the internal audio (Dell XPS 15 9560).
i8kutils issue https://github.com/vitorafsr/i8kutils/issues/15
There is no much thing we can do in the audio driver side, unfortunately.
There is zero connection between dell-smm-hwmon and usb-audio from OS POV, hence it's likely an issue about BIOS command execution in the hardware level.
Better to ask dell-smm-hwmon people instead, I guess.
The only solution I am aware of is to not use i8kutils, and/or to blacklist the dell-smm-hwmon driver. Executing BIOS code on Dell machines, as the i8k code does, effectively stops the kernel for a significant amount of time. This is a limitation of the SMM BIOS on those systems; there is nothing we can do about it. It is not surprising that this results in audible clicks.
Well, at least I can document this hardware limitation and reference this issue. It should help people to work around it.
Thanks for your timely feedback.