Re: [PATCH v2 2/2] arm64: dts: meson-t7-a311d2-khadas-vim4: add initial device-tree

[Neil Armstrong]

On 21/06/2023 10:01, Conor Dooley wrote:
> On Wed, Jun 21, 2023 at 08:37:02AM +0100, Lucas Tanure wrote:
> > On Wed, Jun 21, 2023 at 7:02 AM Krzysztof Kozlowski
> > <krzysztof.kozlowski@xxxxxxxxxx> wrote:
> > > On 21/06/2023 00:09, Yixun Lan wrote:
> > > > > +            apb4: bus@fe000000 {
> > > > > +                    compatible = "simple-bus";
> > > > > +                    reg = <0x0 0xfe000000 0x0 0x480000>;
> > > > > +                    #address-cells = <2>;
> > > > > +                    #size-cells = <2>;
> > > > > +                    ranges = <0x0 0x0 0x0 0xfe000000 0x0 0x480000>;
> > > > > +
> > > > > +                    uart_A: serial@78000 {
> > > > > +                            compatible = "amlogic,meson-t7-uart",
> > > >                                                ~~~~~~~~~~~~~~~~~
> > > > if you introduce new compatible string, then at least you need to document it
> > > > so Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml need to be updated
> > > >
> > > > but my qeustion here, why bother introducing new compatible string if nothing
> > > > changed with the compatible data? given the uart is same IP with g12a, can't we just
> > > > use "amlogic,meson-g12-uart" for this? no only it will reduce the structure length of
> > > > meson_uart_dt_match[], but also relieve maintainer's review burden?
> > >
> > > https://elixir.bootlin.com/linux/v6.1-rc1/source/Documentation/devicetree/bindings/writing-bindings.rst#L42
> > >
> > > Best regards,
> > > Krzysztof
> > Hi, I did not understand the recommendation here.
> > Can I add "amlogic,meson-t7-uart" without Documentation changes?
>
> No, you can't.
>
> > I think Yes, as I can see a few compatible strings in dts that don't
> > exist anywhere else.
>
> Aye, but we do not want to propagate that. New stuff should not be
> adding undocumented compatibles, and those that are undocumented should
> be documented.

Documentation is ongoing, it takes time !

Neil

> > My idea here is to add "amlogic,meson-t7-uart" for future use if ever
> > created, like if we find a bug in the future that is only relevant to
> > T7 soc.
> > But for now, fallback to s4 uart, as it seems to be the same controller.
> >
> > >From Krzysztof said in the writing-bindings.rst, I am following the rules.
> >
> > So, what's the path forward here?
>
> You are following the rules from the dts point of view, you just need a
> 3rd patch in which you document the pattern you have added here in
> amlogic,meson-uart.yaml. It is probably something like:
> +      - items:
> +          - const: amlogic,meson-t7-uart
> +          - const: amlogic,meson-s4-uart
> But I have not tested that, I just wrote that in my mail client.
>
> Cheers,
> Conor.