0001 # SPDX-License-Identifier: GPL-2.0-only
0002 %YAML 1.2
0003 ---
0004 $id: http://devicetree.org/schemas/i2c/i2c-mux-gpio.yaml#
0005 $schema: http://devicetree.org/meta-schemas/core.yaml#
0006
0007 title: GPIO-based I2C Bus Mux
0008
0009 maintainers:
0010 - Wolfram Sang <wsa@kernel.org>
0011
0012 description: |
0013 This binding describes an I2C bus multiplexer that uses GPIOs to route the I2C signals.
0014
0015 +-----+ +-----+
0016 | dev | | dev |
0017 +------------+ +-----+ +-----+
0018 | SoC | | |
0019 | | /--------+--------+
0020 | +------+ | +------+ child bus A, on GPIO value set to 0
0021 | | I2C |-|--| Mux |
0022 | +------+ | +--+---+ child bus B, on GPIO value set to 1
0023 | | | \----------+--------+--------+
0024 | +------+ | | | | |
0025 | | GPIO |-|-----+ +-----+ +-----+ +-----+
0026 | +------+ | | dev | | dev | | dev |
0027 +------------+ +-----+ +-----+ +-----+
0028
0029 For each I2C child node, an I2C child bus will be created. They will be numbered based on their
0030 order in the device tree.
0031
0032 Whenever an access is made to a device on a child bus, the value set in the relevant node's reg
0033 property will be output using the list of GPIOs, the first in the list holding the least-
0034 significant value.
0035
0036 If an idle state is defined, using the idle-state (optional) property, whenever an access is not
0037 being made to a device on a child bus, the GPIOs will be set according to the idle value.
0038
0039 If an idle state is not defined, the most recently used value will be left programmed into
0040 hardware whenever no access is being made to a device on a child bus.
0041
0042 properties:
0043 compatible:
0044 const: i2c-mux-gpio
0045
0046 i2c-parent:
0047 description: phandle of the I2C bus that this multiplexer's master-side port is connected to
0048 $ref: "/schemas/types.yaml#/definitions/phandle"
0049
0050 mux-gpios:
0051 description: list of GPIOs used to control the muxer
0052 minItems: 1
0053 maxItems: 4 # Should be enough
0054
0055 idle-state:
0056 description: Value to set the muxer to when idle. When no value is given, it defaults to the
0057 last value used.
0058 $ref: "/schemas/types.yaml#/definitions/uint32"
0059
0060 allOf:
0061 - $ref: i2c-mux.yaml
0062
0063 unevaluatedProperties: false
0064
0065 required:
0066 - compatible
0067 - i2c-parent
0068 - mux-gpios
0069
0070 examples:
0071 - |
0072 i2cmux {
0073 compatible = "i2c-mux-gpio";
0074 #address-cells = <1>;
0075 #size-cells = <0>;
0076 mux-gpios = <&gpio1 22 0>, <&gpio1 23 0>;
0077 i2c-parent = <&i2c1>;
0078
0079 i2c@1 {
0080 reg = <1>;
0081 #address-cells = <1>;
0082 #size-cells = <0>;
0083
0084 ssd1307: oled@3c {
0085 compatible = "solomon,ssd1307fb-i2c";
0086 reg = <0x3c>;
0087 pwms = <&pwm 4 3000>;
0088 reset-gpios = <&gpio2 7 1>;
0089 };
0090 };
0091
0092 i2c@3 {
0093 reg = <3>;
0094 #address-cells = <1>;
0095 #size-cells = <0>;
0096
0097 pca9555: pca9555@20 {
0098 compatible = "nxp,pca9555";
0099 gpio-controller;
0100 #gpio-cells = <2>;
0101 reg = <0x20>;
0102 };
0103 };
0104 };
