Adding PPS on Jetson Orin with Pin 31

[yezelin2018]

I am trying to add a PPS pin on Jetson AGX Orin. Here is my procedure:

1. Pin31, GPIO3_PAA.00 is a default GPIO input pin, I planned to use this as the pin for PPS.
2. Under /Linux_for_Tegra/kernel/dtb, decompile the tegra234-p3701-0000-p3737-0000.dtb to a dts file using dtc: sudo dtc -O dts tegra234-p3701-0000-p3737-0000.dtb -o c.dts
3. Add PPS to the dts file:

pps {
		gpios = <0x13C 0x0 0x1>;
		compatible = "pps-gpio";
		assert-falling-edge;
		status = "okay";
	};

For the hex number in gpios, I assume 0x13C refers to the base address for the tegra_aon_gpio, and 0x0 refers to the Pin AA.00, 0x1 is the GPIO_ACTIVE_LOW (I wonder if this setting is correct, if not what should be the right way to set it)

4. recompile the dts to dtb with sudo dtc -O dtb c.dts -o tegra234-p3701-0000-p3737-0000.dtb
5. flash the Orin using ./flash.sh within Linux_for_Tegra
   Got and error:

[    4.609612] OF: /pps: could not get #gpio-cells for /aconnect@2a41000/ahub/ports/port@71/endpoint
[    4.618730] pps-gpio pps: failed to request PPS GPIO
[    4.623827] pps-gpio: probe of pps failed with error -22
[    4.629986] device-mapper: uevent: version 1.0.3

Could someone show me the correct way to set it up, thanks!!

[JerryChang]

hello yezelin2018,

please see-also these two forum topics, such as…
Unable to achieve PPS with Jetpack 5.0.2 - #7 by mhtechdev,
HOW to Increase GNNS timing module on Xavier? - #9 by shgarg