RPi 4, 8Gb, Ubuntu 20.04, PoE Hat Fan Speed Control

[johnjamesjacoby]

Hey there. First new topic; long time anonymous lurker. Apologies if this is not the correct forum.

I recently installed Ubuntu 20.04 on an 8Gb Raspberry Pi 4, and am powering it via an official PoE Hat. It appears to be working correctly, except the dtparam overrides in /boot/firmware/usercfg.txt do not appear to have any effect.

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# PoE Hat Fan Speeds
dtparam=poe_fan_temp0=65000,poe_fan_temp0_hyst=5000
dtparam=poe_fan_temp1=67000,poe_fan_temp1_hyst=2000

The above overrides work correctly in Raspberry Pi OS in /boot/config.txt on several Raspberry Pi 3B's and 4's.

Any ideas?

[wildestpixel]

I'm actually seeing some odd behaviour from my POE HAT (albeit I replaced the fan with a Noctua 5v). I'm attributing my odd behaviour to new kernel or possibly bootloaders introduced over the last few weeks.

My dtparam settings no longer have the desired effect. If I don;'t set anything, the fan always seems to be on, and if I set something (like the example you have given) the fan seems to activate at 50 celcius with an hysteris of 2 celsius, so on my Pi 4 4GB 32 setup this ting is on and off like a yoyo whilst idling at the desktop (just serving vnc)

Something changed as I had previously for a long time had these settings running perfectly (i.e. since about August last year)

Some observations are made here : https://github.com/raspberrypi/linux/issues/2715

[wildestpixel]

Looks like from some testing that adding the line at the beginning fo this section so that for examplke your settings read :

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dtoverlay=rpi-poe
dtparam=poe_fan_temp0=57000
dtparam=poe_fan_temp1=60000
dtparam=poe_fan_temp2=63000
dtparam=poe_fan_temp3=66000

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dtoverlay=rpi-poe

* seems to be the magic bullet *