Re: [PATCH v5 1/7] dt-bindings: connector: Add mikrobus-connector

[Rob Herring <robh@kernel.org>]

On Wed, Sep 4, 2024 at 12:09 PM Ayush Singh <ayush@beagleboard.org> wrote:
>
> >> gpio-map is what you are looking for. It's documented in the DT spec.
> >> It was created exactly for this purpose of remapping GPIO lines on a
> >> connector.
> >>
> >> Rob
>
>
> Hi. I found docs on nexus nodes [1] and tried using it for mikroBUS, but
> it does not seem to be working. Here is my connector:
>
> ```
>
>      mikrobus_gpio0: mikrobus-gpio0 {
>          #gpio-cells = <2>;
>          gpio-map =
>          <0 0 &main_gpio1 11 0>, <1 0 &main_gpio1 9 0>,
>          <2 0 &main_gpio1 24 0>, <3 0 &main_gpio1 25 0>,
>          <4 0 &main_gpio1 22 0>, <5 0 &main_gpio1 23 0>,
>          <6 0 &main_gpio1 7 0>, <7 0 &main_gpio1 8 0>,
>          <8 0 &main_gpio1 14 0>, <9 0 &main_gpio1 13 0>,
>          <10 0 &main_gpio1 12 0>, <11 0 &main_gpio1 10 0>;
>          gpio-map-mask = <0xf 0x0>;
>          gpio-map-pass-thru = <0x0 0x1>;
>      };
>
> ...
>
> &main_uart5 {
>      status = "okay";
>      pinctrl-names = "default";
>      pinctrl-0 = <&mikrobus_uart_pins_default>;
>
>      gnss {
>          compatible = "u-blox,neo-8";
>          reset-gpios = <&mikrobus_gpio0 10 GPIO_ACTIVE_LOW>;
>      };
> };
>
> ```
>
>
> After some fdtdump, I can see that at least the dtc compiler does not
> seem to do the forwarding at dt compile time. Here is the dump:

dtc knows nothing about it.

> ```
>
> mikrobus-gpio0 {
>          #gpio-cells = <0x00000002>;
>          gpio-map = <0x00000000 0x00000000 0x00000025 0x0000000b
> 0x00000000 0x00000001 0x00000000 0x00000025 0x00000009 0x00000000
> 0x00000002 0x00000000 0x00000025 0x00000018 0x00000000 0x00000003
> 0x00000000 0x00000025 0x00000019 0x00000000 0x00000004 0x00000000
> 0x00000025 0x00000016 0x00000000 0x00000005 0x00000000 0x00000025
> 0x00000017 0x00000000 0x00000006 0x00000000 0x00000025 0x00000007
> 0x00000000 0x00000007 0x00000000 0x00000025 0x00000008 0x00000000
> 0x00000008 0x00000000 0x00000025 0x0000000e 0x00000000 0x00000009
> 0x00000000 0x00000025 0x0000000d 0x00000000 0x0000000a 0x00000000
> 0x00000025 0x0000000c 0x00000000 0x0000000b 0x00000000 0x00000025
> 0x0000000a 0x00000000>;
>          gpio-map-mask = <0x0000000f 0x00000000>;
>          gpio-map-pass-thru = <0x00000000 0x00000001>;
>          phandle = <0x0000000e>;
>      };

You might need "gpio-controller" here. Though if you do, I think
that's a mistake in the kernel. It should work like interrupt-map and
generally you have either interrupt-controller or interrupt-map, but
not both (though that is allowed now too).

> ...
>
> serial@2850000 {
>              compatible = "ti,am64-uart", "ti,am654-uart";
>              reg = <0x00000000 0x02850000 0x00000000 0x00000100>;
>              interrupts = <0x00000000 0x000000b7 0x00000004>;
>              power-domains = <0x00000003 0x0000009c 0x00000001>;
>              clocks = <0x00000002 0x0000009c 0x00000000>;
>              clock-names = "fclk";
>              status = "okay";
>              pinctrl-names = "default";
>              pinctrl-0 = <0x0000000d>;
>              phandle = <0x00000081>;
>              gnss {
>                  compatible = "u-blox,neo-8";
>                  reset-gpios = <0x0000000e 0x0000000a 0x00000001>;
>              };
>   };
>
> ```
>
>
> So I am a bit unsure. Is the dtc parser in the kernel supposed to do the

No such thing as "dtc parser in the kernel".

> mapping, or is it supposed to be done by `dtc` at compile time?

No.

> Maybe we
> do not have support for it in upstream kernel yet?

Yes, there is upstream support. Grep for of_parse_phandle_with_args_map.

Rob