Re: [PATCH v1 1/8] dt-bindings: pinctrl: Add thead,th1520-pinctrl bindings

[Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>]

Rob Herring wrote:
> On Fri, Dec 15, 2023 at 03:38:59PM +0100, Emil Renner Berthing wrote:
> > Add bindings for the pin controllers on the T-Head TH1520 RISC-V SoC.
> >
> > Signed-off-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
> > ---
> >  .../pinctrl/thead,th1520-pinctrl.yaml         | 156 ++++++++++++++++++
> >  1 file changed, 156 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/pinctrl/thead,th1520-pinctrl.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/pinctrl/thead,th1520-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/thead,th1520-pinctrl.yaml
> > new file mode 100644
> > index 000000000000..1b1b446cd498
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pinctrl/thead,th1520-pinctrl.yaml
> > @@ -0,0 +1,156 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pinctrl/thead,th1520-pinctrl.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: T-Head TH1520 SoC pin controller
> > +
> > +maintainers:
> > +  - Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
> > +
> > +description: |
> > +  Pinmux and pinconf controller in the T-Head TH1520 RISC-V SoC.
> > +
> > +  The TH1520 has 3 groups of pads each controlled from different memory ranges.
> > +  Confusingly the memory ranges are named
> > +    PADCTRL_AOSYS  -> PAD Group 1
> > +    PADCTRL1_APSYS -> PAD Group 2
> > +    PADCTRL0_APSYS -> PAD Group 3
>
> Are the programming models different?

Yes, they control different pads and different number of pads. Pad group 1 also
has some special pins that have bespoke pinconf, no pinconf and/or no
pinmux and a
"gap" in the registers. Also if some day we'll need to set up pinmux
on behald of the
audio co-processor then pad group 1 will be even more special.

> > +
> > +  Each pad can be muxed individually to up to 5 different functions. For most
> > +  pads only a few of those 5 configurations are valid though, and a few pads in
> > +  group 1 does not support muxing at all.
> > +
> > +  Pinconf is fairly regular except for a few pads in group 1 that either can't
> > +  be configured or has some special functions. The rest have configurable drive
> > +  strength, input enable, schmitt trigger, slew rate, pull-up and pull-down in
> > +  addition to a special strong pull up.
> > +
> > +  Certain pads in group 1 can be muxed to AUDIO_PA0 - AUDIO_PA30 functions and
> > +  are then meant to be used by the audio co-processor. Each such pad can then
> > +  be further muxed to either audio GPIO or one of 4 functions such as UART, I2C
> > +  and I2S. If the audio pad is muxed to one of the 4 functions then pinconf is
> > +  also configured in different registers. All of this is done from a different
> > +  AUDIO_IOCTRL memory range and is left to the audio co-processor for now.
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - thead,th1520-group1-pinctrl
> > +      - thead,th1520-group2-pinctrl
> > +      - thead,th1520-group3-pinctrl
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +patternProperties:
> > +  '-[0-9]+$':
>
> Please make this a bit more specific. "-grp-[0-9]+$"?

Oh, I was just trying to copy what other drivers did, but I see now that eg.
mediatek,mt6779-pinctrl is not in the majority. Unfortunately "group" already
has 2 meanings in this context. One are the pad groups from the datasheet
described above and then there are the mux groups in the pinctrl framework,
which in this case just contains a single pin since each pin can be muxed
individually. Can we come up with a better name or should we just add this 3rd
type of group?

> > +    patternProperties:
> > +      '-pins$':
> > +        type: object
> > +        $ref: /schemas/pinctrl/pincfg-node.yaml
> > +        description:
> > +          A pinctrl node should contain at least one subnode describing one
> > +          or more pads and their associated pinmux and pinconf settings.
> > +
> > +        properties:
> > +          pins:
> > +            $ref: /schemas/types.yaml#/definitions/string-array
>
> Type is defined in pinmux-node.yaml. You need to reference it and drop
> this.
>
> Normally the possible values are listed out.

This seems to work for me:

allOf:
  - if:
      properties:
        compatible:
          const: thead,th1520-group1-pinctrl
    then:
      patternProperties:
        '-[0-9]+$':
          patternProperties:
            '-pins$':
              properties:
                pins:
                  items:
                    enum:
                      - OSC_CLK_IN
                      - OSC_CLK_OUT
		      ...
  - if:
      properties:
        compatible:
          const: thead,th1520-group2-pinctrl
    then:
      patternProperties:
        '-[0-9]+$':
          patternProperties:
            '-pins$':
              properties:
                pins:
                  items:
                    enum:
                      - QSPI1_SCLK
                      - QSPI1_CSN0
		      ...
  ...

Would that be the way to go about it?

> > +            description: List of pads that properties in the node apply to.
> > +
> > +          function:
> > +            $ref: /schemas/types.yaml#/definitions/string
> > +            enum: [ "0", "1", "2", "3", "4", "5" ]
> > +            description: The mux function to select for the given pins.
> > +
> > +          bias-disable: true
> > +
> > +          bias-pull-up:
> > +            type: boolean
> > +
> > +          bias-pull-down:
> > +            type: boolean
> > +
> > +          drive-strength:
> > +            enum: [ 1, 2, 3, 5, 7, 8, 10, 12, 13, 15, 16, 18, 20, 21, 23, 25 ]
> > +
> > +          input-enable: true
> > +
> > +          input-disable: true
> > +
> > +          input-schmitt-enable: true
> > +
> > +          input-schmitt-disable: true
> > +
> > +          slew-rate:
> > +            maximum: 1
> > +
> > +          thead,strong-pull-up:
> > +            oneOf:
> > +              - type: boolean
> > +              - $ref: /schemas/types.yaml#/definitions/uint32
> > +                enum: [ 0, 2100 ]
> > +            description: Enable or disable strong 2.1kOhm pull-up.
>
> bias-pull-up can already specify the strength in Ohms.

The strong pull up is a separate bit that can be enabled independently from the
regular pull-up/down, so in theory you could enable both the regular pull-up
and the strong pull-up at the same time, or even the regular poll-down and the
strong pull-up which is probably not advised.
So the idea here was just to make sure that you can do eg.

	thead,strong-pull-up = <0>;

to make sure the bit is cleared.

Thanks!
/Emil