Re: [PATCH v6 04/15] dt-bindings: add BCM6328 pincontroller binding documentation

[Rob Herring <robh+dt@kernel.org>]

On Wed, Mar 10, 2021 at 11:03 AM Álvaro Fernández Rojas
<noltari@gmail.com> wrote:
>
> Hi Rob,
>
> > El 10 mar 2021, a las 18:45, Rob Herring <robh+dt@kernel.org> escribió:
> >
> > On Wed, Mar 10, 2021 at 5:55 AM Álvaro Fernández Rojas
> > <noltari@gmail.com> wrote:
> >>
> >> Add binding documentation for the pincontrol core found in BCM6328 SoCs.
> >>
> >> Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
> >> Co-developed-by: Jonas Gorski <jonas.gorski@gmail.com>
> >> Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
> >> ---
> >> v6: add changes suggested by Rob Herring
> >> v5: change Documentation to dt-bindings in commit title
> >> v4: no changes
> >> v3: add new gpio node
> >> v2: remove interrupts
> >>
> >> .../pinctrl/brcm,bcm6328-pinctrl.yaml         | 174 ++++++++++++++++++
> >> 1 file changed, 174 insertions(+)
> >> create mode 100644 Documentation/devicetree/bindings/pinctrl/brcm,bcm6328-pinctrl.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/pinctrl/brcm,bcm6328-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/brcm,bcm6328-pinctrl.yaml
> >> new file mode 100644
> >> index 000000000000..471f6efa1754
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/pinctrl/brcm,bcm6328-pinctrl.yaml
> >> @@ -0,0 +1,174 @@
> >> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/pinctrl/brcm,bcm6328-pinctrl.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Broadcom BCM6328 pin controller
> >> +
> >> +maintainers:
> >> +  - Álvaro Fernández Rojas <noltari@gmail.com>
> >> +  - Jonas Gorski <jonas.gorski@gmail.com>
> >> +
> >> +description: |+
> >> +  The pin controller node should be the child of a syscon node.
> >> +
> >> +  Refer to the the bindings described in
> >> +  Documentation/devicetree/bindings/mfd/syscon.yaml
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: brcm,bcm6328-pinctrl
> >> +
> >> +  gpio:
> >> +    type: object
> >> +    properties:
> >> +      compatible:
> >> +        const: brcm,bcm6328-gpio
> >> +
> >> +      data:
> >> +        $ref: /schemas/types.yaml#/definitions/uint32
> >> +        description: |
> >> +          Offset in the register map for the data register (in bytes).
> >> +
> >> +      dirout:
> >> +        $ref: /schemas/types.yaml#/definitions/uint32
> >> +        description: |
> >> +          Offset in the register map for the dirout register (in bytes).
> >> +
> >> +      gpio-controller: true
> >> +
> >> +      "#gpio-cells":
> >> +        const: 2
> >> +
> >> +      gpio-ranges:
> >> +        maxItems: 1
> >> +
> >> +    required:
> >> +      - gpio-controller
> >> +      - gpio-ranges
> >> +      - '#gpio-cells'
> >> +
> >> +    additionalProperties: false
> >> +
> >> +patternProperties:
> >> +  '^.*-pins$':
> >> +    if:
> >> +      type: object
> >> +    then:
> >> +      properties:
> >> +        function:
> >> +          $ref: "pinmux-node.yaml#/properties/function"
> >> +          enum: [ serial_led_data, serial_led_clk, inet_act_led, pcie_clkreq,
> >> +                  led, ephy0_act_led, ephy1_act_led, ephy2_act_led,
> >> +                  ephy3_act_led, hsspi_cs1, usb_device_port, usb_host_port ]
> >> +
> >> +        pins:
> >> +          $ref: "pinmux-node.yaml#/properties/pins"
> >> +          enum: [ gpio6, gpio7, gpio11, gpio16, gpio17, gpio18, gpio19,
> >> +                  gpio20, gpio25, gpio26, gpio27, gpio28, hsspi_cs1,
> >> +                  usb_port1 ]
> >> +
> >> +required:
> >> +  - compatible
> >> +  - gpio
> >> +
> >> +additionalProperties: false
> >> +
> >> +examples:
> >> +  - |
> >> +    gpio_cntl@10000080 {
> >> +      compatible = "brcm,bcm6328-gpio-controller", "syscon", "simple-mfd";
> >
> > You just added "brcm,bcm6328-gpio-controller", it would need to be documented.
>
> I just added that because you requested me to do it ¯\_(ツ)_/¯

I said 'syscon' by itself was not allowed, then asked about the multiple levels.

> What should I do to document it?
> I still don’t get most of this .yaml stuff...
>
> >
> >> +      reg = <0x10000080 0x80>;
> >> +
> >> +      pinctrl: pinctrl {
> >> +        compatible = "brcm,bcm6328-pinctrl";
> >> +
> >> +        gpio {
> >> +          compatible = "brcm,bcm6328-gpio";
> >
> > I'm still trying to understand why you need 3 levels of nodes here?
> > The gpio controller contains a pin controller plus other undefined
> > functions (because of 'syscon') and the pin controller contains a gpio
> > controller?
>
> In previous versions the gpio controller was registered along with the pin controller, but @Linus requested me to register the gpio pin controller ranges through device tree by using gpio-ranges and I decided to use this approach, which was already used by other pin controllers.
> However, there aren’t any pinctrl drivers using gpio-regmap, so this is kind of new…
>
> >
> > I think "brcm,bcm6328-gpio-controller" and "brcm,bcm6328-pinctrl"
> > should be a single node.
>
> I agree, but does it make sense to add gpio-ranges to a pinctrl node referencing itself?

It wouldn't be. I wasn't saying the pinctrl and gpio controller are
the same node. My suggestion was combining syscon and pinctrl.

> Something like:
> syscon {

Again with the syscon. If pinctrl and GPIO are the only functions
within this h/w block, then this is not a syscon. You are just abusing
that having 'syscon' compatible means you get a regmap created
automagically for you. Nothing here looks like a 'system controller'
to me. A 'system controller' is a random collection of register bits
with functions that don't fit anywhere else.

>         pinctrl: pinctrl {
>                 compatible …
>
>                 gpio-controller;
>                 gpio-ranges = <&pinctrl 0 0 32>;
>                 #gpio-cells = <2>;

I was assuming you have multiple GPIO controllers within 1 pinctlr?
The pinctrl and gpio could be a single node like above if there's only
1 GPIO controller. But I'm still somewhat guessing what the h/w looks
like because I have to go searching thru the driver to decipher.
Please describe the h/w in the binding.

If there's more than 1 GPIO controller, then I'd imagine you have
something like this:

pinctrl {
  ...
  reg = <base 0x80>;
  ranges = <0 base 0x80;
  gpio@4 {
    reg = <4 4>, <c 4>;
    reg-names = "dirout", "dat";
  };
  gpio@? {};

  foo-pins {};
};

>
>                 …
>         };
> };
>
> >
> >> +          data = <0xc>;
> >> +          dirout = <0x4>;
> >
> > This looks similar to the brcm,bcm6345-gpio.txt binding which then
> > uses the gpio-mmio driver. Defining addresses with 'reg' is much
> > preferred over custom properties. That binding also captures the bank
> > size.
>
> It’s similar, but Linus requested to use gpio regmap because we had a large amount of registers, so we’re not using it.

Looks like you have 2 registers to me.

Rob