Specifying intricate driver dependency ordering for regulators and components

[asteriskSF]

I have a system I'm working on that requires a complicated device init ordering. This project is using zephyr 3.4 from Nordics NCS 2.5.2.

The system has 2 voltage regulators each with an enable. One regulator has the enable tied to a native (on-chip) gpio. This provides one voltage rail (3V3). this voltage rail must be enabled to provide power for an I/O expander, which has an output for the second voltage regulator.

So the init sequence must be:

enable regulator_3V3 via gpio0

init io_expander

configure regulator output on io_expander

enable regulator_5V via io_expander

init peripherals downstream from regulator_5V (via level shifter)

The problem I see is that voltage regulators all get assigned the same init priority, so I don't see how I would be able to init one regulator before the io_expander and the other regulator after the io_expander.

Is there a way to do this?

Best approach I have come up with is to duplicate the regulator_fixed driver into a second driver that I could then assign a different init priority.

Also I saw some discussion from 2020 about making the driver init order based on dependencies, does that work? Even if it does, how would I indicate the dependency between the regulator and the devices it powers?

[bmulder-innoseis]

@asteriskSF I have the exact same problem, but with an i2c bus between the MCU and the I/O expander, while another i2c bus should be turned off using the regulator.
Did you manage to find a solution to this problem yet?
I was thinking that deferred init might be the way to go here. But it basically means almost all of my devices in the tree need deferred init. So if there is a more elegant, config-only solution I'd like to hear that, too.

In fact, it would be nice if you could specify an init priority in the device tree, not inside C code or KConfig (which is unified if you use two of the same devices)
They did something related in #58297 but I'm not sure in what version of Zephyr they released it (I'm still on 3.7) and if it fixes these complex cases