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

[Rob Herring <robh+dt@xxxxxxxxxx>]

On Thu, Mar 11, 2021 at 10:09 AM Álvaro Fernández Rojas
<noltari@xxxxxxxxx> wrote:
>
> Hi Rob,
>
> El 10/03/2021 a las 21:52, Rob Herring escribió:
> > On Wed, Mar 10, 2021 at 12:10 PM Álvaro Fernández Rojas
> > <noltari@xxxxxxxxx> wrote:
> >>
> >> Hi Rob,
> >>
> >>> El 10 mar 2021, a las 19:45, Rob Herring <robh+dt@xxxxxxxxxx> escribió:
> >>>
> >>> On Wed, Mar 10, 2021 at 11:03 AM Álvaro Fernández Rojas
> >>> <noltari@xxxxxxxxx> wrote:
> >>>>
> >>>> Hi Rob,
> >>>>
> >>>>> El 10 mar 2021, a las 18:45, Rob Herring <robh+dt@xxxxxxxxxx> escribió:
> >>>>>
> >>>>> On Wed, Mar 10, 2021 at 5:55 AM Álvaro Fernández Rojas
> >>>>> <noltari@xxxxxxxxx> wrote:
> >>>>>>
> >>>>>> Add binding documentation for the pincontrol core found in BCM6328 SoCs.
> >>>>>>
> >>>>>> Signed-off-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
> >>>>>> Co-developed-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
> >>>>>> Signed-off-by: Álvaro Fernández Rojas <noltari@xxxxxxxxx>
> >>>>>> ---
> >>>>>> 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@xxxxxxxxx>
> >>>>>> +  - Jonas Gorski <jonas.gorski@xxxxxxxxx>
> >>>>>> +
> >>>>>> +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.
> >>
> >> Why not?
> >
> > Because 'syscon' alone doesn't mean anything and doesn't describe what
> > registers it contains. You need something that says this is the XYZ
> > block in the ABC SoC.
> >
> >> What if you have several controllers inside a syscon?
> >
> > You either just add properties (e.g. just add #clock-cells and it's a
> > clock provider) or you have child nodes. Which one you do generally
> > depends on if the providers have DT resources themselves.
> >
> >> The root should also have “something" in it?
> >>
> >>>
> >>>> What should I do to document it?
>
> You didn't answer my question about adding documentation...

You have to document it. Whether it's 1 or 3 schema files depends on
where we end up, but the top-level one should reference the others if
it's more than 1 file:

child-node:
  type: object
  $ref: "/schemas/foo/child-node.yaml#"

> An example driver which adds a custom compatible string and doesn't
> document it:
> https://github.com/torvalds/linux/blob/a74e6a014c9d4d4161061f770c9b4f98372ac778/Documentation/devicetree/bindings/clock/sprd%2Csc9863a-clk.yaml#L90

*it Happens.

Those cases are now blocking my adding a check that they are
undocumented. There's no shortage of examples of what not to do.

>
> >>>> 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.
> >>
> >> But that wouldn’t be correct if there were more “things” inside the syscon, right?
> >
> > Right.
> >
> >>>> 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 and GPIO aren’t the only functions within this HW block.
> >> Maybe I didn’t document/code it properly, but I’m sure I’m not abusing what a system controller is.
> >
> > Okay, that's the detail missing from this patch.
> >
> >> Please, take a look at http://www.datashed.science/misc/bcm/gpl/broadcom-sdk-416L05/shared/opensource/include/bcm963xx/6328_map_part.h:
> >> typedef struct GpioControl {
> >>      uint32      GPIODirHi;                  /* 0 */
> >>      uint32      GPIODir;                    /* 4 */
> >>      uint32      GPIOioHi;                   /* 8 */
> >>      uint32      GPIOio;                     /* C */
> >>      uint32      unused0;                    /* 10 */
> >>      uint32      SpiSlaveCfg;                /* 14 */
> >>      uint32      GPIOMode;                   /* 18 */
> >>      uint64      PinMuxSel;                  /* 1C */
> >>      uint32      PinMuxSelOther;             /* 24 */
> >>      uint32      TestControl;                /* 28 */
> >>      uint32      unused2;                    /* 2C */
> >>      uint32      RoboSWLEDControl;           /* 30 */
> >>      uint32      RoboSWLEDLSR;               /* 34 */
> >>      uint32      unused3;                    /* 38 */
> >>      uint32      RoboswEphyCtrl;             /* 3C */
> >>      uint32      RoboswSwitchCtrl;           /* 40 */
> >>      uint32      RegFileTmCtl;               /* 44 */
> >>      uint32      RingOscCtrl0;               /* 48 */
> >>      uint32      RingOscCtrl1;               /* 4C */
> >>      uint32      unused4[6];                 /* 50 - 64 */
> >>      uint32      DieRevID;                   /* 68 */
> >>      uint32      unused5;                    /* 6c */
> >>      uint32      DiagSelControl;             /* 70 */
> >>      uint32      DiagReadBack;               /* 74 */
> >>      uint32      DiagReadBackHi;             /* 78 */
> >>      uint32      DiagMiscControl;            /* 7c */
> >> } GpioControl;
> >>
> >> So we’re using GPIODirHi, GPIODir, GPIOioHi and GPIOio registers for GPIO regmap driver.
> >> And we’re using GPIOMode, PinMuxSel (u64 -> x2 u32), PinMuxSelOther for pinctrl driver.
> >> And this is for BCM6328, but some of the other SoCs are even more scattered.
> >
> > So based on this I'd do something like this:
> >
> > syscon {
> >    reg = <base 0x80>;
> >    ranges = <0 base 0x80>;
> >    pinctrl@18 {
> >      reg = <0x18 0x10>;
> >      foo-pins {};
> >    gpio@0 {
> >      reg = <0x0 0x10>;
> >    };
> > };
>
> You're missing a "};", so I'm not sure if you want me to go this way (1):
> syscon {
>         compatible = "brcm,bcm6328-gpio-regs", "syscon", "simple-mfd";
>         reg = <0x10000080 0x80>;
>         ranges = <0 0x10000080 0x80>;
>
>         gpio: gpio@0 {
>                 compatible = "brcm,bcm6328-gpio";
>                 reg = <0x0 0x10>;
>
>                 data = <0xc>;
>                 dirout = <0x4>;
>
>                 gpio-controller;
>                 gpio-ranges = <&pinctrl 0 0 32>;
>                 #gpio-cells = <2>;
>         };
>
>         pinctrl: pinctrl@18 {
>                 compatible = "brcm,bcm6328-pinctrl";
>                 reg = <0x18 0x10>;
>
>                 foo-pins {};
>                 ...
>         };
> };

This way.

>
> Or this way (2):
> syscon {
>         compatible = "brcm,bcm6328-gpio-regs", "syscon", "simple-mfd";
>         reg = <0x10000080 0x80>;
>         ranges = <0 0x10000080 0x80>;
>
>         pinctrl: pinctrl@18 {
>                 compatible = "brcm,bcm6328-pinctrl";
>                 reg = <0x0 0x28>;
>
>                 gpio: gpio@0 {

This doesn't make sense IMO because GPIO is not a sub-function of the
pinctrl h/w. They are peers.

>                         compatible = "brcm,bcm6328-gpio";
>                         reg = <0x0 0x10>;
>
>                         data = <0xc>;
>                         dirout = <0x4>;
>
>                         gpio-controller;
>                         gpio-ranges = <&pinctrl 0 0 32>;
>                         #gpio-cells = <2>;
>                 };
>
>                 foo-pins {};
>                 ...
>         };
> };