Re: [PATCH v2 11/16] dt-bindings: pinctrl: Add StarFive JH7100 bindings

[Linus Walleij <linus.walleij@linaro.org>]

On Thu, Oct 21, 2021 at 7:42 PM Emil Renner Berthing <kernel@esmil.dk> wrote:

> Add bindings for the StarFive JH7100 GPIO/pin controller.
>
> Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>

That is a very terse commit message for an entirely new
SoC, please put a little blurb about this silicon there.
Like mention that it is RISC-V at least.

Overall quite interesting!

> +$id: http://devicetree.org/schemas/pinctrl/starfive,jh7100-pinctrl.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: StarFive JH7100 Pin Controller Device Tree Bindings
> +
> +maintainers:
> +  - Emil Renner Berthing <kernel@esmil.dk>
> +  - Drew Fustini <drew@beagleboard.org>

Add description: talking about that this is a RISC-V SoC
and other implicit things that are really good to know.

> +  starfive,signal-group:
> +    description: |
> +      The SoC has a global setting selecting one of 7 different pinmux
> +      configurations of the pads named GPIO[0:63] and FUNC_SHARE[0:141]. After
> +      this global setting is chosen only the 64 "GPIO" pins can be further
> +      muxed by configuring them to be controlled by certain peripherals rather
> +      than software.
> +      Note that in configuration 0 none of GPIOs are routed to pads, and only
> +      in configuration 1 are the GPIOs routed to the pads named GPIO[0:63].
> +      If this property is not set it defaults to the configuration already
> +      chosen by the earlier boot stages.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [0, 1, 2, 3, 4, 5, 6]

This still is hard for me to understand. Does it mean that 0..6 define
how the direct-to-peripheral-pins are set up?

Then it would make sense to describe what happens for 0, 1, 2 ...6
i.e. what the different set-ups are.

Actually this is what we call group-based pin multiplexing in Linux,
this property seems to avoid using that concept.
See for example:
Documentation/devicetree/bindings/pinctrl/cortina,gemini-pinctrl.txt

> +    patternProperties:
> +      '-pins*$':
> +        type: object
> +        description: |
> +          A pinctrl node should contain at least one subnode representing the
> +          pinctrl groups available on the machine. Each subnode will list the
> +          pins it needs, and how they should be configured, with regard to
> +          muxer configuration, bias, input enable/disable, input schmitt
> +          trigger enable/disable, slew-rate and drive strength.
> +        $ref: "/schemas/pinctrl/pincfg-node.yaml"

Nice that you use pincfg-node.yaml

> +        properties:
> +          pins:
> +            description: |
> +              The list of pin identifiers that properties in the node apply to.
> +              This should be set using either the PAD_GPIO or PAD_FUNC_SHARE
> +              macro. Either this or "pinmux" has to be specified.
> +
> +          pinmux:
> +            description: |
> +              The list of GPIO identifiers and their mux settings that
> +              properties in the node apply to. This should be set using the
> +              GPIOMUX macro. Either this or "pins" has to be specified.

What about referencing
Documentation/devicetree/bindings/pinctrl/pinmux-node.yaml
for this?

Yours,
Linus Walleij