Quoting "Gary E. Miller" <g...@rellim.com>:
Good stuff, but I find no mention of GPIO timestamping..
pps-gpio takes the timestamp in the kernel interrupt handler.
The code is here:
http://lxr.free-electrons.com/source/drivers/pps/clients/pps-gpio.c?v=4.6#L60
To do this, the GPIO peripheral in the BCM2835 is configured to
interrupt on an edge, with this code:
http://lxr.free-electrons.com/source/drivers/pinctrl/bcm/pinctrl-bcm2835.c?v=4.5#L416
GPREN0 / GPFEN0 are defined in
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf
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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