Fix: PiKVM RPi4 (4gb) official RPi POE+ hat fan failure

1) Enter read/write mode

[root@pikvm ~]# rw

2) Edit raspberrypi.conf in nano

nano /etc/modules-load.d/raspberrypi.conf

Comment out or remove snd-bcm2835 and add i2c_dev to a new line

File contents:

#snd-bcm2835
i2c_dev

Save and exit nano

ctrl + x, y, enter

3) Create a new systemd service, pikvm-poe-plus-fix.service

nano /etc/systemd/system/pikvm-poe-plus-fix.service

File contents:

[Unit]
Description=Fix RPi4 (4gb) official RPi POE+ hat fan failure

[Service]
ExecStart=/usr/local/bin/pikvm-bridge-fan-fix.sh

[Install]
WantedBy=multi-user.target

Save and exit nano

ctrl + x, y, enter

Set permissions to -rw-r--r--

chmod 644 /etc/systemd/system/pikvm-poe-plus-fix.service

4) Create file pikvm-bridge-fan-fix.sh

nano /usr/local/bin/pikvm-bridge-fan-fix.sh

File contents:

#!/bin/sh
sleep 30
i2cdetect -y 0

Save and exit

ctrl + x, y, enter

Set permissions to -rwxr-xr-x, making it executable

chmod 755 /usr/local/bin/pikvm-bridge-fan-fix.sh

5) Reload systemd manager configuration

systemctl daemon-reload

6) Test the new service

systemctl start pikvm-poe-plus-fix.service

Wait 30 seconds for the timer to complete

7) Check the service status

systemctl status pikvm-poe-plus-fix.service

The output should look something like this:

[root@pikvm ~]# systemctl status pikvm-poe-plus-fix.service
* pikvm-poe-plus-fix.service - Fix RPi4 (4gb) official RPi POE+ hat fan failure
  Loaded: loaded (/etc/systemd/system/pikvm-poe-plus-fix.service; enabled; vendor preset: disabled)
  Active: inactive (dead) since Wed 2021-12-01 03:41:44 MSK; 3 days ago
 Process: 349 ExecStart=/usr/local/bin/pikvm-bridge-fan-fix.sh (code=exited, status=0/SUCCESS)
Main PID: 349 (code=exited, status=0/SUCCESS)
     CPU: 47ms

Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 00:                         -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab pikvm-bridge-fan-fix.sh[454]: 70: -- -- -- -- -- -- -- --
Dec 01 03:41:44 pikvm.lab sudo[450]: pam_unix(sudo:session): session closed for user root
Dec 01 03:41:44 pikvm.lab systemd[1]: pikvm-poe-plus-fix.service: Deactivated successfully.

Exit systemctl

ctrl + c

8) Set the service to start on boot

systemctl enable pikvm-poe-plus-fix.service

9) Return to read only mode

ro

10) Reboot your system

reboot

If successful, your KVM should work and the rpi poe+ fan will spin up once it reaches temp!