I’ve been digging through the numberous articles on getting PPS support working on various carrier boards. I think i’m getting close, but need some help decyphering how the DTS file gets updated and how it know which GPIO to use.
Firstly, I’ve got tegra_defconfig setup with:
and my DTS file contains:
gpios = <&tegra_main_gpio 216 0>;
compatable = “pps-gpio”;
status = “okay”;
I am attempting to use GPIO 216 from the spacely GPIO expansion header.
It calls out P00 on P13 (pin 15), sysfs # 216. But the Pin is sourced via a TCA9539 at address 0x77.
I can’t find any reference in any of the Connect Tech DTS files that would show assigning one of the expansion GPIO to a special function like this.
My guess is my selection of the pin via the tegra_gpio_main 216 0 is wrong. Now looking through other DTS files, i can find:
status = “disabled”;
Does my pps section need to reside inside the gpio@77? does anyone have any experience in how to assign a gpio pin from a port expander to the pps gpio cell?
any help is appreciated.