Zephyr GPIO initialization before HW drivers

[Morten Sabinsky]

Hi 

I am working on a nRF52840 using Zephyr as OS.

I have setup some control GPIO pins in the device tree (se below). This works fine from the application. I can access the definitions and set GPIOs in the states I want.

My issue is that I need the control pins to be in a specific state before Zephyr initializes the HW drivers. 

Can you control the sequence of driver initialization in zephyr? 

Is there a way to initialize GPIO states in the device tree?

Or put some GPIO initialization in before HW drivers are initialized?

I have been searching but not found the correct rabbit hole yet, so any help/pointers are appreciated.

Morten Sabinsky

Device tree setup

++ Snip

gpio_list: node {
compatible = "gpio_defs";
gpios = <&gpio0 6 GPIO_ACTIVE_HIGH >, // 0: Control pin 0
<&gpio0 7 GPIO_ACTIVE_HIGH >, // 1: Control pin 1
<&gpio0 8 GPIO_ACTIVE_LOW >, // 2: Control pin 2
};

++ Snip

/* GPIO support */
&gpiote {
status = "okay";
};

&gpio0 {
status = "okay";
};

[Håkon Alseth]

Hi,

 

GPIOs that needs to be set prior to initialization usually gets placed in a PRE_KERNEL system init, like done here for the nrf9160dk_nrf52840 board.c file:

https://github.com/nrfconnect/sdk-zephyr/blob/master/boards/arm/nrf9160dk_nrf52840/board.c#L217-L240

 

The problem with setting a gpio before the "zephyr gpio" driver is initialized is that you cannot use the zephyr driver instance to set it, so you need to use the nrf_gpio.h (or other bare metal implementations) to configure/set. It isn't clear if this is a restriction in your case, or if you want to set these before communicating with an external IC or similar.

 

If you require setting this with a higher priority than another module (ie. in a situation where zephyr's gpio is already inited), you can look at the sys_init() macro for the module in question, and setup one that happens before it: https://docs.zephyrproject.org/latest/reference/drivers/index.html#c.SYS_INIT

 

Kind regards,

Håkon

[Morten Sabinsky]

Thanks this is what i needed

Morten

[Håkon Alseth]

Glad to hear that, Morten!

Let me know if you run into any issues.

 

Cheers,

Håkon