Re: [PATCH 1/6] dt-bindings: mfd: add binding for Apple Mac System Management Controller

[Rob Herring <robh+dt@xxxxxxxxxx>]

On Thu, Sep 1, 2022 at 10:56 AM Russell King (Oracle)
<linux@xxxxxxxxxxxxxxx> wrote:
>
> On Thu, Sep 01, 2022 at 06:45:52PM +0300, Krzysztof Kozlowski wrote:
> > On 01/09/2022 18:24, Russell King (Oracle) wrote:
> > > On Thu, Sep 01, 2022 at 06:15:46PM +0300, Krzysztof Kozlowski wrote:
> > >> On 01/09/2022 18:12, Russell King (Oracle) wrote:
> > >>>>> +  compatible:
> > >>>>> +    items:
> > >>>>> +      - enum:
> > >>>>> +        - apple,t8103-smc
> > >>>>
> > >>>> You miss two spaces of indentation on this level.
> > >>>
> > >>> Should that be picked up by the dt checker?

I have a problem that Krzysztof is quicker. ;) Maybe I should stop
screening the emails (for the times I break things mostly).

> > >>
> > >> I think yamllint complains about it. It is not a hard-dependency, so
> > >> maybe you don't have it installed.
> > >>
> > >>>
> > >>>>> +        - apple,t8112-smc
> > >>>>> +        - apple,t6000-smc
> > >>>>
> > >>>> Bring some order here - either alphabetical or by date of release (as in
> > >>>> other Apple schemas). I think t6000 was before t8112, so it's none of
> > >>>> that orders.
> > >>>
> > >>> Ok.
> > >>>
> > >>>>> +      - const: apple,smc
> > >>>>> +
> > >>>>> +  reg:
> > >>>>> +    description: Two regions, one for the SMC area and one for the SRAM area.
> > >>>>
> > >>>> You need constraints for size/order, so in this context list with
> > >>>> described items.
> > >>>
> > >>> How do I do that? I tried maxItems/minItems set to 2, but the dt checker
> > >>> objected to it.
> > >>
> > >> One way:
> > >> reg:
> > >>   items:
> > >>     - description: SMC area
> > >>     - description: SRAM area
> > >>
> > >> but actually this is very similar what you wrote for reg-names - kind of
> > >> obvious, so easier way:
> > >>
> > >> reg:
> > >>   maxItems: 2
> > >
> > > Doesn't work. With maxItems: 2, the example fails, yet it correctly lists
> > > two regs which are 64-bit address and 64-bit size - so in total 8 32-bit
> > > ints.
> > >
> > > Documentation/devicetree/bindings/mfd/apple,smc.example.dtb: smc@23e400000: reg: [[2, 1044381696], [0, 16384], [2, 1071644672], [0, 1048576]] is too long
> > >         From schema: /home/rmk/git/linux-rmk/Documentation/devicetree/bindings/mfd/apple,smc.yaml
> > >
> > > Hence, I originally had maxItems: 2, and ended up deleting it because of
> > > the dt checker.
> > >
> > > With the two descriptions, it's the same failure.
> >
> > Yeah, they should create same result.
> >
> > >
> > > I think the problem is that the checker has no knowledge in the example
> > > of how big each address and size element of the reg property is. So,
> > > it's interpreting it as four entries of 32-bit address,size pairs
> > > instead of two entries of 64-bit address,size pairs. Yep, that's it,
> > > if I increase the number of "- description" entries to four then it's
> > > happy.
> > >
> > > So, what's the solution?
> > >
> >
> > If you open generated DTS examples (in your
> > kbuild-output/Documentation/devicetree/bindings/mfd/) you will see which
> > address/size cells are expected. By default it is I think address/size
> > cells=1, so you need a bus node setting it to 2.
>
> Thanks, that works. The patch with all those points addressed now looks
> like:
>
> 8<===
> From: "Russell King (Oracle)" <rmk+kernel@xxxxxxxxxxxxxxx>
> Subject: [PATCH] dt-bindings: mfd: add binding for Apple Mac System Management
>  Controller
>
> Add a DT binding for the Apple Mac System Management Controller.
>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
> ---
>  .../devicetree/bindings/mfd/apple,smc.yaml    | 61 +++++++++++++++++++
>  1 file changed, 61 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/apple,smc.yaml
>
> diff --git a/Documentation/devicetree/bindings/mfd/apple,smc.yaml b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
> new file mode 100644
> index 000000000000..168f237c2962
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
> @@ -0,0 +1,61 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/apple,smc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Apple Mac System Management Controller
> +
> +maintainers:
> +  - Hector Martin <marcan@xxxxxxxxx>
> +
> +description:
> +  Apple Mac System Management Controller implements various functions
> +  such as GPIO, RTC, power, reboot.
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - apple,t6000-smc
> +          - apple,t8103-smc
> +          - apple,t8112-smc
> +      - const: apple,smc
> +
> +  reg:
> +    items:
> +      - description: SMC area
> +      - description: SRAM area

Based on the disjoint addresses, is this really one device? Perhaps
the SRAM area should use mmio-sram binding? That already supports
sub-dividing the sram for different uses. I'll comment more on the
full example.

Rob