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

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Date:   Mon, 25 Oct 2021 01:11:06 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Emil Renner Berthing <kernel@...il.dk>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        Drew Fustini <drew@...gleboard.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michael Zhu <michael.zhu@...rfivetech.com>,
        Fu Wei <tekkamanninja@...il.com>,
        Anup Patel <anup.patel@....com>,
        Atish Patra <atish.patra@....com>,
        Matteo Croce <mcroce@...rosoft.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 11/16] dt-bindings: pinctrl: Add StarFive JH7100 bindings

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

> Add bindings for the StarFive JH7100 GPIO/pin controller.
>
> Signed-off-by: Emil Renner Berthing <kernel@...il.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@...il.dk>
> +  - Drew Fustini <drew@...gleboard.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