Regulators from GPIO expander

[Neunz]

Hi, 

I have some dependency issues in my devicetree definition. 

I have a first regulator that control the power of a gpio expander connected through I2C. 

This GPIO expander control other regulators, for other devices. 

It seems that all regulators declared from gpio expander try to get configured before the gpio expander is initialized. 

But I need the first regulator to be initialized before the gpio expander. 

What is the recommended way to implement this initialization order. 

First regulator -> I2C -> GPIO expander -> other regulators ? 

[Øyvind]

Hello, 

Can you please provide more information and elaborate more on what you are trying to achieve. What device are you using? What version of nRF Connect SDK are you using?

Thank you.
Kind regards,
Øyvind

[Neunz]

I'm on nrf Connect v1.9. 

It's a custom board with a NRF52840. 

I use one GPIO for enabling power for the most important peripherals.

I added a regulator in my device tree, this regulator is enabled by this GPIO. 

Then I have a PCA9534 GPIO expander on I2C. 

I want to add more regulators managed by the pins from the GPIO expander.

Here sample of my device tree and an overlay I use for regulators from GPIO expander : 

/ {
	
	sw_3v3_en: sw-3v3-ctrl {
		compatible = "regulator-fixed-sync", "regulator-fixed";
		label = "sw-3v3-ctrl";
		regulator-name = "sw-3v3-ctrl";
		enable-gpios = <&gpio1 12 GPIO_ACTIVE_HIGH>;
		/* Always on in dev config */ 
		regulator-boot-on;
	};

    [...]
    
};

/ {

    en_a_aux: en-a-ctrl {
		compatible = "regulator-fixed";
		label = "PERIPHERAL-A-REGULATOR";
		regulator-name = "en-a-ctrl";
		enable-gpios = <&gpio_expander 0 GPIO_ACTIVE_HIGH>;
        vin-supply = <&sw_3v3_en>;
		// Always on in dev config
		regulator-boot-on;
	};
};

&i2c1 {
    gpio_expander: tca953x@20 {
        status = "okay";
        compatible = "ti,tca9538";
        label = "PCA953X";
        reg = <0x20>;
        gpio-controller;
        ngpios = <8>;
        #gpio-cells = <2>;
        vin-supply = <&sw_3v3_en>;
    };
};

Regards,

[Øyvind]

Thank you for providing this information. Unfortunately, I am not familiar with the Zephyr regulator subsystem. The closest application I can think of, that uses the regulator subsystem, is the Thingy:52. Have a look at the board files found under zephyr\boards\arm\thingy52_nrf52832\ in the SDK. Board.c configures the power rails at start-up and might be a good starting point for your application.

You may also get better answers regarding the Devicetree and Zephyr specific system in the Zephyr Community support on Discord

Kind regards,
Øyvind

[Neunz]

Thank you for your time. 

I will find my way on the Zephyr Community. 

Regards, 

[Øyvind]

Good luck! If you are not able to find your answers there, let me know and I will see what we can do here. 

Kind regards,
Øyvind