xref: /openbmc/linux/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.yaml (revision 8b82b841)

# SPDX-License-Identifier: GPL-2.0-only
%YAML 1.2
---
$id: http://devicetree.org/schemas/i2c/i2c-mux-pinctrl.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Pinctrl-based I2C Bus Mux

maintainers:
  - Wolfram Sang <wsa@kernel.org>

description: |
  This binding describes an I2C bus multiplexer that uses pin multiplexing to route the I2C
  signals, and represents the pin multiplexing configuration using the pinctrl device tree
  bindings.

                                 +-----+  +-----+
                                 | dev |  | dev |
    +------------------------+   +-----+  +-----+
    | SoC                    |      |        |
    |                   /----|------+--------+
    |   +---+   +------+     | child bus A, on first set of pins
    |   |I2C|---|Pinmux|     |
    |   +---+   +------+     | child bus B, on second set of pins
    |                   \----|------+--------+--------+
    |                        |      |        |        |
    +------------------------+  +-----+  +-----+  +-----+
                                | dev |  | dev |  | dev |
                                +-----+  +-----+  +-----+

  For each named state defined in the pinctrl-names property, an I2C child bus will be created.
  I2C child bus numbers are assigned based on the index into the pinctrl-names property.

  The only exception is that no bus will be created for a state named "idle". If such a state is
  defined, it must be the last entry in pinctrl-names. For example:

    pinctrl-names = "ddc", "pta", "idle"  ->  ddc = bus 0, pta = bus 1
    pinctrl-names = "ddc", "idle", "pta"  ->  Invalid ("idle" not last)
    pinctrl-names = "idle", "ddc", "pta"  ->  Invalid ("idle" not last)

  Whenever an access is made to a device on a child bus, the relevant pinctrl state will be
  programmed into hardware.

  If an idle state is defined, whenever an access is not being made to a device on a child bus,
  the idle pinctrl state will be programmed into hardware.

  If an idle state is not defined, the most recently used pinctrl state will be left programmed
  into hardware whenever no access is being made of a device on a child bus.

properties:
  compatible:
    const: i2c-mux-pinctrl

  i2c-parent:
    $ref: /schemas/types.yaml#/definitions/phandle
    description: The phandle of the I2C bus that this multiplexer's master-side port is connected
      to.

allOf:
  - $ref: i2c-mux.yaml

unevaluatedProperties: false

required:
  - compatible
  - i2c-parent

examples:
  - |
    i2cmux {
      compatible = "i2c-mux-pinctrl";
      #address-cells = <1>;
      #size-cells = <0>;

      i2c-parent = <&i2c1>;

      pinctrl-names = "ddc", "pta", "idle";
      pinctrl-0 = <&state_i2cmux_ddc>;
      pinctrl-1 = <&state_i2cmux_pta>;
      pinctrl-2 = <&state_i2cmux_idle>;

      i2c@0 {
        reg = <0>;
        #address-cells = <1>;
        #size-cells = <0>;

        eeprom@50 {
          compatible = "atmel,24c02";
          reg = <0x50>;
        };
      };

      i2c@1 {
        reg = <1>;
        #address-cells = <1>;
        #size-cells = <0>;

        eeprom@50 {
          compatible = "atmel,24c02";
          reg = <0x50>;
        };
      };
    };