Re: [PATCH v3 02/12] dt-bindings: pinctrl: Add RaspberryPi RP1 gpio/pinctrl/pinmux bindings

[Andrea della Porta <andrea.porta@xxxxxxxx>]

Hi Krzysztof,

On 19:10 Thu 31 Oct     , Krzysztof Kozlowski wrote:
> On 31/10/2024 15:07, Andrea della Porta wrote:
> > Hi Krzysztof,
> > 
> > On 08:26 Tue 29 Oct     , Krzysztof Kozlowski wrote:
> >> On Mon, Oct 28, 2024 at 03:07:19PM +0100, Andrea della Porta wrote:
> >>> Add device tree bindings for the gpio/pin/mux controller that is part of
> >>> the RP1 multi function device, and relative entries in MAINTAINERS file.
> >>>
> >>> Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx>
> >>> ---
> >>>  .../pinctrl/raspberrypi,rp1-gpio.yaml         | 163 ++++++++++++++++++
> >>>  MAINTAINERS                                   |   2 +
> >>>  2 files changed, 165 insertions(+)
> >>>  create mode 100644 Documentation/devicetree/bindings/pinctrl/raspberrypi,rp1-gpio.yaml
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/pinctrl/raspberrypi,rp1-gpio.yaml b/Documentation/devicetree/bindings/pinctrl/raspberrypi,rp1-gpio.yaml
> >>> new file mode 100644
> >>> index 000000000000..465a53a6d84f
> >>> --- /dev/null
> >>> +++ b/Documentation/devicetree/bindings/pinctrl/raspberrypi,rp1-gpio.yaml
> >>> @@ -0,0 +1,163 @@
> >>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >>> +%YAML 1.2
> >>> +---
> >>> +$id: http://devicetree.org/schemas/pinctrl/raspberrypi,rp1-gpio.yaml#
> >>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>> +
> >>> +title: RaspberryPi RP1 GPIO/Pinconf/Pinmux Controller submodule
> >>> +
> >>> +maintainers:
> >>> +  - Andrea della Porta <andrea.porta@xxxxxxxx>
> >>> +
> >>> +description:
> >>> +  The RP1 chipset is a Multi Function Device containing, among other sub-peripherals,
> >>> +  a gpio/pinconf/mux controller whose 54 pins are grouped into 3 banks. It works also
> >>
> >> Please wrap code according to coding style (checkpatch is not a coding
> >> style description but only a tool).
> > 
> > Ack.
> > 
> >>
> >>> +  as an interrupt controller for those gpios.
> >>> +
> >>> +properties:
> >>> +  compatible:
> >>> +    const: raspberrypi,rp1-gpio
> >>> +
> >>> +  reg:
> >>> +    maxItems: 3
> >>> +    description: One reg specifier for each one of the 3 pin banks.
> >>> +
> >>> +  '#gpio-cells':
> >>> +    description: The first cell is the pin number and the second cell is used
> >>> +      to specify the flags (see include/dt-bindings/gpio/gpio.h).
> >>> +    const: 2
> >>> +
> >>> +  gpio-controller: true
> >>> +
> >>> +  gpio-ranges:
> >>> +    maxItems: 1
> >>> +
> >>> +  gpio-line-names:
> >>> +    maxItems: 54
> >>> +
> >>> +  interrupts:
> >>> +    maxItems: 3
> >>> +    description: One interrupt specifier for each one of the 3 pin banks.
> >>> +
> >>> +  '#interrupt-cells':
> >>> +    description:
> >>> +      Specifies the Bank number [0, 1, 2] and Flags as defined in
> >>> +      include/dt-bindings/interrupt-controller/irq.h.
> >>> +    const: 2
> >>> +
> >>> +  interrupt-controller: true
> >>> +
> >>> +additionalProperties:
> >>
> >> Not much improved. You are supposed to have here pattern, just like
> >> other bindings. I asked for this last time.
> >>
> >> And there are examples using it - almost all or most of pinctrl
> >> bindings, including bindings having subnodes (but you do not use such
> >> case here).
> > 
> > This is the same approach used in [1], which seems quite recent. I did't
> 
> 2021, so not that recent, but you are right that it's not the example I
> would recommend. See rather:
> git grep pins -- Documentation/devicetree/bindings/pinctrl/ | grep '\$'
> 
> 
> pins, groups, states, etc.

Perfect. Thanks for the example suggestion.

> 
> > use pattern because I wouldn't really want to enforce a particular naming
> > scheme. Subnodes are used, please see below. Since pinctrl.yaml explicitly
> 
> But we want to enforce, because it brings uniformity and matches
> partially generic naming patterns.

Ack.

> 
> > says that there is no common binding but each device has its own, I
> > thought that was reasonable choice. Should I enforce some common pattern,
> > then?
> 
> Yes, you should. Again, look at other bindings, e.g. qcom tlmm or lpass lpi.

Ok.

> 
> > 
> >>
> >>> +  anyOf:
> >>> +    - type: object
> >>> +      additionalProperties: false
> >>> +      allOf:
> >>> +        - $ref: pincfg-node.yaml#
> >>> +        - $ref: pinmux-node.yaml#
> >>> +
> >>> +      description:
> >>> +        Pin controller client devices use pin configuration subnodes (children
> >>> +        and grandchildren) for desired pin configuration.
> >>> +        Client device subnodes use below standard properties.
> >>> +
> >>> +      properties:
> >>> +        pins:
> >>> +          description:
> >>> +            A string (or list of strings) adhering to the pattern 'gpio[0-5][0-9]'
> >>> +        function: true
> >>> +        bias-disable: true
> >>> +        bias-pull-down: true
> >>> +        bias-pull-up: true
> >>> +        slew-rate:
> >>> +          description: 0 is slow slew rate, 1 is fast slew rate
> >>> +          enum: [ 0, 1 ]
> >>> +        drive-strength:
> >>> +          enum: [ 2, 4, 8, 12 ]
> >>> +
> >>> +    - type: object
> >>> +      additionalProperties:
> >>> +        $ref: "#/additionalProperties/anyOf/0"
> >>
> >> Your example does not use any subnodes, so this looks not needed.
> > 
> > The example has subnodes, as in the following excerpt from the example:
> 
> I meant, you do not need properties in subnodes (1st level). You only
> want properties in subnodes of subnodes, so 2nd level. What is the point
> of allowing them in 1st level?

I will add those two sub-nodes to the example:

            rp1-i2s0-default-state {
                function = "i2s0";
                pins = "gpio18", "gpio19", "gpio20", "gpio21";
                bias-disable;
            };

            rp1-uart0-default-state {
                txd-pins {
                    function = "uart0";
                    pins = "gpio14";
                    bias-disable;
                };

                rxd-pins {
                    function = "uart0";
                    pins = "gpio15";
                    bias-pull-up;
                };
            };

The first is just a group of pins with the same settings, the second is 
a pin group with different settings per pin. This is basically the same
usage as in qcom,sm4250-lpass-lpi-pinctrl.yaml.

Many thanks,
Andrea

 
> 
> 
> 
> Best regards,
> Krzysztof
>