On Thu, Apr 21, 2022 at 10:16 AM Michael Walle <michael@xxxxxxxx> wrote:
>
> Am 2022-04-21 16:23, schrieb Rob Herring:
>
> > What's needed here is a connector node (and driver) for the mikrobus
> > socket. The connector node's purpose is to decouple the host DT from
> > add-on board overlay DT. Something like this:
>
> Funny I had a similar idea to have a connector with all the
> properties, but I failed to see how that would be of any help.
>
> Do you mind an example of such an overlay? Judging by the spi
> and i2c subnode, I guess it will amend the connector node and
> fill in it's devices?
Right.
>
> And all the child device properties will reference the connector,
> correct?
Right.
>
> > connector {
> > // And a more specific compatible if pins can have alt funcs?
> > // Spec version needed?
> > compatible = "mikrobus-socket";
> >
> > // Will need regulators defined if child devices expect
> > // regulators
> > vcc-33-supply = <®33>;
> > vcc-5-supply = <®5v>;
> >
> > i2c-parent = <&i2c1>; // Already a defined property
> > spi-parent = <&spi0>; // New
>
> uart/serial needed too?
Yes. Serial has the extra issue in the kernel that tty vs. serdev are
mutually exclusive and decided by presence or not of a child node for
the UART. That would need some work to dynamically switch. I think I
have some old patches doing that, but they probably break some aspects
of TTY expectations.
>
> >
> > // RST pin
> > reset-gpios = <&gpio 4 0>;
> >
> > // remap 'INT' (index 0) to host interrupt
> > #interrupt-cells = <2>;
> > #address-cells = <0>;
> > interrupt-map = <0 0 &gpio 3 0>;
> >
> > spi {
>
> For example:
>
> my-device@0 {
> reg = <0>; // really needed? there is only one SPI CS line
Yes, needed.
> compatible = "my-device";
> reset-gpios = // may be left unset if it's optional, but what
> // what if it is a required property and in hardware
> // its connected to the RST pin of the module?
Probably should not be required and the connector driver manages it.
> other-gpios = <&connector 2>;
> vdd-supply = // what comes here? <&connector VCC_33>?
That has to be figured out, but *-supply doesn't take arg cells
currently. Probably the connector needs to define its own regulator
nodes.
> interrupts-extended = <&connector 0 ..>;
> }
Rob
