Hi Linus,
On Thu, Oct 12, 2023 at 09:25:20AM +0200, Linus Walleij wrote:
> On Tue, Oct 10, 2023 at 7:25???AM AKASHI Takahiro
> <takahiro.akashi@xxxxxxxxxx> wrote:
>
> > > We can probably mandate that this has to be inside a pin controller
> > > since it is a first.
> >
> > Yeah, my U-Boot implementation tentatively supports both (inside and
> > outside pin controller). But it is not a user's choice, but we should
> > decide which way to go.
>
> OK I have decided we are going to put it inside the pin control node,
> as a subnode. (I don't expect anyone to object.)
While I'm still thinking of how I can modify my current implementation
to fit into 'inside' syntax, there are a couple of concerns:
1) invoke gpiochip_add_data() at probe function
Probably we no longer need "compatible" property, but instead we need to
call gpiochip_add_data() explicitly in SCMI pin controller's probe
as follows:
scmi_pinctrl_probe()
...
devm_pinctrl_register_and_init(dev, ..., pctrldev);
pinctrl_enable(pctrldev);
device_for_each_child_node(dev, fwnode)
if (fwnode contains "gpio-controller") {
/* what pin_control_gpio_probe() does */
gc->get_direction = ...;
...
devm_gpiochip_data_add(dev, gc, ...);
}
2) gpio-by-pinctrl.c
While this file is SCMI-independent now, due to a change at (1),
it would be better to move the whole content inside SCMI pin controller
driver (because there is no other user for now).
3) Then, pin-control-gpio.yaml may also be put into SCMI binding
(i.e. firmware/arm,scmi.yaml). Can we leave the gpio binding outside?
4) phandle in "gpio-ranges" property
(As you mentioned)
The first element in a tuple of "gpio-ranges" is a phandle to a pin
controller node. Now that the gpio node is a sub node of pin controller,
the phandle is trivial. But there is no easier way to represent it
than using an explicit label:
(My U-Boot implementation does this.)
scmi {
...
scmi_pinctrl: protocol@19 {
...
gpio {
gpio-controller;
...
gpio-ranges = <&scmi_pinctrl ... >;
}
}
}
I tried:
gpio-ranges = <0 ...>; // dtc passed, but '0' might be illegal by spec.
gpio-ranges = <(-1) ...>; // dtc passed, but ...
gpio-ranges = <&{..} ...>; // dtc error because it's not a full path.
Do you have any other idea? Otherwise, I will modify my RFC
with the changes above.
-Takahiro Akashi
> It makes everything easier and clearer for users I think.
>
> Yours,
> Linus Walleij
