ktrainor
Posts: 7
Joined: Tue Dec 04, 2012 7:04 pm

PoE HAT Fans not operating on two Raspberry Pi 4s

Mon Feb 15, 2021 9:25 pm

Hi All,

I apologize for cross-posting this.

I am experiencing inactive fans on two Raspberry Pi 4 machines with PoE Hat installed. Relevant dmesg output on both is:

[ 4.976242] rpi-poe-fan rpi-poe-fan@0: Failed to get default PWM value: -5
[ 4.976278] rpi-poe-fan: probe of rpi-poe-fan@0 failed with error -5

On both machines, the fan does not start when the machine boots. The fan does not run whether or not I have entries in /boot/config.txt to control the fan speed. It looks like both fans have simply stopped working. They had been working reliably for about 4 months on both systems.

I updated the OS on both of these machines last week. I am very suspicious that the OS update broke the PoE Hat fan integration.

Does anyone have any suggestions about fixes? Workarounds?

Thanks in advance for your help.

Best Regards,

Kevin

ok3000
Posts: 1
Joined: Tue Feb 16, 2021 10:36 am

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Tue Feb 16, 2021 10:49 am

i had the same problem after updating my raspberrypi 4 yesterday and here I found the solution:

[Solved] PoE HAT fan failed to get default PWM value
viewtopic.php?f=53&t=298985#p1815221

Code: Select all

sudo SKIP_KERNEL=1 rpi-update 32f92809
for me the downgrading worked and fan is as loud as before :D

ktrainor
Posts: 7
Joined: Tue Dec 04, 2012 7:04 pm

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Tue Feb 16, 2021 4:48 pm

Thanks. That worked on both machines!

I am assuming that this is a short-term workaround. I am trying to figure out how to account for it in my workflow. I just received 8 new Raspberry Pi 4 8GB machines that will make up a little experimental research computing cluster. I need to provision all 8 of them. I guess that I could load and update the OS as usual. Then, I could downgrade the firmware. Do you think that there might be a more direct path to the same place?

Best,

Kevin

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 12154
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Tue Feb 16, 2021 8:25 pm

The fix is already in the main rpi-update branch, so just doing "sudo rpi-update" should get you the latest kernel and firmware with the POE HAT fan working fine.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.


ktrainor
Posts: 7
Joined: Tue Dec 04, 2012 7:04 pm

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Thu Feb 25, 2021 6:03 pm

I provisioned one of my new Raspberry Pi 4s. The fan problem was still present even though I ran:

* sudo apt update
* sudo apt full-upgrade

I realize that these are different commands than the one that you recommended. But, I did expect them to work.

In order to get my fan working, I still needed to back off the firmware upgrade. Am I just using the wrong commands to update my OS? Or, is there possibly more to this?

Best,

Kevin

User avatar
rpdom
Posts: 19287
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Thu Feb 25, 2021 6:45 pm

The fix is not in the apt versions yet, which is why 6by9 said to use rpi-update if you want it. rpi-update is not usually recommended as it loads the very latest version of kernel and firmware and may have changes that have not been fully tested yet (that's what rpi-update is for - to install the latest versions for people to test). apt has the versions that have been through the testing phases.
Unreadable squiggle

ktrainor
Posts: 7
Joined: Tue Dec 04, 2012 7:04 pm

Re: PoE HAT Fans not operating on two Raspberry Pi 4s

Fri Feb 26, 2021 3:26 pm

Thanks. I never quite understood the difference between these two update approaches.

Return to “HATs and other add-ons”