0001 Pinctrl-based I2C Bus DeMux
0002
0003 This binding describes an I2C bus demultiplexer that uses pin multiplexing to
0004 route the I2C signals, and represents the pin multiplexing configuration using
0005 the pinctrl device tree bindings. This may be used to select one I2C IP core at
0006 runtime which may have a better feature set for a given task than another I2C
0007 IP core on the SoC. The most simple example is to fall back to GPIO bitbanging
0008 if your current runtime configuration hits an errata of the internal IP core.
0009
0010 +-------------------------------+
0011 | SoC |
0012 | | +-----+ +-----+
0013 | +------------+ | | dev | | dev |
0014 | |I2C IP Core1|--\ | +-----+ +-----+
0015 | +------------+ \-------+ | | |
0016 | |Pinctrl|--|------+--------+
0017 | +------------+ +-------+ |
0018 | |I2C IP Core2|--/ |
0019 | +------------+ |
0020 | |
0021 +-------------------------------+
0022
0023 Required properties:
0024 - compatible: "i2c-demux-pinctrl"
0025 - i2c-parent: List of phandles of I2C masters available for selection. The first
0026 one will be used as default.
0027 - i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C
0028 parents.
0029
0030 Furthermore, I2C mux properties and child nodes. See i2c-mux.yaml in this
0031 directory.
0032
0033 Example:
0034
0035 Here is a snipplet for a bus to be demuxed. It contains various i2c clients for
0036 HDMI, so the bus is named "i2c-hdmi":
0037
0038 i2chdmi: i2c@8 {
0039
0040 compatible = "i2c-demux-pinctrl";
0041 i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
0042 i2c-bus-name = "i2c-hdmi";
0043 #address-cells = <1>;
0044 #size-cells = <0>;
0045
0046 ak4643: sound-codec@12 {
0047 compatible = "asahi-kasei,ak4643";
0048
0049 #sound-dai-cells = <0>;
0050 reg = <0x12>;
0051 };
0052
0053 composite-in@20 {
0054 compatible = "adi,adv7180";
0055 reg = <0x20>;
0056 remote = <&vin1>;
0057
0058 port {
0059 adv7180: endpoint {
0060 bus-width = <8>;
0061 remote-endpoint = <&vin1ep0>;
0062 };
0063 };
0064 };
0065
0066 hdmi@39 {
0067 compatible = "adi,adv7511w";
0068 reg = <0x39>;
0069 interrupt-parent = <&gpio1>;
0070 interrupts = <15 IRQ_TYPE_LEVEL_LOW>;
0071
0072 adi,input-depth = <8>;
0073 adi,input-colorspace = "rgb";
0074 adi,input-clock = "1x";
0075 adi,input-style = <1>;
0076 adi,input-justification = "evenly";
0077
0078 ports {
0079 #address-cells = <1>;
0080 #size-cells = <0>;
0081
0082 port@0 {
0083 reg = <0>;
0084 adv7511_in: endpoint {
0085 remote-endpoint = <&du_out_lvds0>;
0086 };
0087 };
0088
0089 port@1 {
0090 reg = <1>;
0091 adv7511_out: endpoint {
0092 remote-endpoint = <&hdmi_con>;
0093 };
0094 };
0095 };
0096 };
0097 };
0098
0099 And for clarification, here are the snipplets for the i2c-parents:
0100
0101 gpioi2c: i2c@9 {
0102 #address-cells = <1>;
0103 #size-cells = <0>;
0104 compatible = "i2c-gpio";
0105 gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */
0106 &gpio5 5 GPIO_ACTIVE_HIGH /* scl */
0107 >;
0108 i2c-gpio,delay-us = <5>;
0109 };
0110
0111 ...
0112
0113 &i2c2 {
0114 pinctrl-0 = <&i2c2_pins>;
0115 pinctrl-names = "i2c-hdmi";
0116
0117 clock-frequency = <100000>;
0118 };
0119
0120 ...
0121
0122 &iic2 {
0123 pinctrl-0 = <&iic2_pins>;
0124 pinctrl-names = "i2c-hdmi";
0125
0126 clock-frequency = <100000>;
0127 };
0128
0129 Please note:
0130
0131 - pinctrl properties for the parent I2C controllers need a pinctrl state
0132 with the same name as i2c-bus-name, not "default"!
0133
0134 - the i2c masters must have their status "disabled". This driver will
0135 enable them at runtime when needed.
