PPS Device on APU2C4

Hi !

i have some RPi4 running with a gps device and the connected PPS Signal to one of the gpio pins.
Now im thinking about “copying” this to ipfire (im using a APU2C3/4 Board which has also GPIO Pins)
I saw on startup of ipfire

Blockquote
Mar 13 16:40:49 ipfire kernel: pps_core: LinuxPPS API ver. 1 registered
Mar 13 16:40:49 ipfire kernel: pps pps0: new PPS source ptp0
Mar 13 16:40:49 ipfire kernel: pps pps1: new PPS source ptp1
Mar 13 16:40:49 ipfire kernel: pps pps2: new PPS source ptp2

So 2 questions…
How i can enable in ipfire using a GPIO Pin as a PPS source…

Gruss Gerd