Kernel PPS processing

Dan Drown dan-ntp at
Tue Jul 5 00:27:50 UTC 2016

Quoting "Gary E. Miller" <gem at>:
> Good stuff, but I find no mention of GPIO timestamping..

pps-gpio takes the timestamp in the kernel interrupt handler.

The code is here:

To do this, the GPIO peripheral in the BCM2835 is configured to  
interrupt on an edge, with this code:

GPREN0 / GPFEN0 are defined in

as "GPIO Falling Edge Detect Enable Registers (GPRENn)"
and "GPIO Rising Edge Detect Enable Registers (GPRENn)"

You can also see the interrupt in the proc filesystem:

$ grep pps /proc/interrupts
170:     900414          0          0          0  pinctrl-bcm2835   4  
Edge      pps.-1

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