linux/Documentation/devicetree/bindings/pinctrl/pinmux-node.yaml

# SPDX-License-Identifier: GPL-2.0-only
%YAML 1.2
---
$id: http://devicetree.org/schemas/pinctrl/pinmux-node.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Generic pin multiplexing node schema

maintainers:
  - Linus Walleij <linus.walleij@linaro.org>

description: |
  The contents of the pin configuration child nodes are defined by the binding
  for the individual pin controller device. The pin configuration nodes need not
  be direct children of the pin controller device; they may be grandchildren,
  for example. Whether this is legal, and whether there is any interaction
  between the child and intermediate parent nodes, is again defined entirely by
  the binding for the individual pin controller device.

  While not required to be used, there are 3 generic forms of pin muxing nodes
  which pin controller devices can use.

  pin multiplexing nodes:

  Example:

  state_0_node_a {
    uart0 {
      function = "uart0";
      groups = "u0rxtx", "u0rtscts";
    };
  };
  state_1_node_a {
    spi0 {
      function = "spi0";
      groups = "spi0pins";
    };
  };
  state_2_node_a {
    function = "i2c0";
    pins = "mfio29", "mfio30";
  };

  Optionally an alternative binding can be used if more suitable depending on the
  pin controller hardware. For hardware where there is a large number of identical
  pin controller instances, naming each pin and function can easily become
  unmaintainable. This is especially the case if the same controller is used for
  different pins and functions depending on the SoC revision and packaging.

  For cases like this, the pin controller driver may use pinctrl-pin-array helper
  binding with a hardware based index and a number of pin configuration values:

  pincontroller {
    ... /* Standard DT properties for the device itself elided */
    #pinctrl-cells = <2>;

    state_0_node_a {
      pinctrl-pin-array = <
        0 A_DELAY_PS(0) G_DELAY_PS(120)
        4 A_DELAY_PS(0) G_DELAY_PS(360)
        ...
        >;
    };
    ...
  };

  Above #pinctrl-cells specifies the number of value cells in addition to the
  index of the registers. This is similar to the interrupts-extended binding with
  one exception. There is no need to specify the phandle for each entry as that
  is already known as the defined pins are always children of the pin controller
  node. Further having the phandle pointing to another pin controller would not
  currently work as the pinctrl framework uses named modes to group pins for each
  pin control device.

  The index for pinctrl-pin-array must relate to the hardware for the pinctrl
  registers, and must not be a virtual index of pin instances. The reason for
  this is to avoid mapping of the index in the dts files and the pin controller
  driver as it can change.

  For hardware where pin multiplexing configurations have to be specified for
  each single pin the number of required sub-nodes containing "pin" and
  "function" properties can quickly escalate and become hard to write and
  maintain.

  For cases like this, the pin controller driver may use the pinmux helper
  property, where the pin identifier is provided with mux configuration settings
  in a pinmux group. A pinmux group consists of the pin identifier and mux
  settings represented as a single integer or an array of integers.

  The pinmux property accepts an array of pinmux groups, each of them describing
  a single pin multiplexing configuration.

  pincontroller {
    state_0_node_a {
      pinmux = <PINMUX_GROUP>, <PINMUX_GROUP>, ...;
    };
  };

  Each individual pin controller driver bindings documentation shall specify
  how pin IDs and pin multiplexing configuration are defined and assembled
  together in a pinmux group.

properties:
  function:
    $ref: /schemas/types.yaml#/definitions/string
    description: The mux function to select

  pins:
    oneOf:
      - $ref: /schemas/types.yaml#/definitions/uint32-array
      - $ref: /schemas/types.yaml#/definitions/string-array
    description:
      The list of pin identifiers that properties in the node apply to. The
      specific binding for the hardware defines whether the entries are integers
      or strings, and their meaning.

  groups:
    $ref: /schemas/types.yaml#/definitions/string-array
    description:
      the group to apply the properties to, if the driver supports
      configuration of whole groups rather than individual pins (either
      this, "pins" or "pinmux" has to be specified)

  pinmux:
    description:
      The list of numeric pin ids and their mux settings that properties in the
      node apply to (either this, "pins" or "groups" have to be specified)
    $ref: /schemas/types.yaml#/definitions/uint32-array

  pinctrl-pin-array:
    $ref: /schemas/types.yaml#/definitions/uint32-array