136 lines
3.3 KiB
Plaintext
136 lines
3.3 KiB
Plaintext
Pinctrl-based I2C Bus DeMux
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This binding describes an I2C bus demultiplexer that uses pin multiplexing to
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route the I2C signals, and represents the pin multiplexing configuration using
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the pinctrl device tree bindings. This may be used to select one I2C IP core at
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runtime which may have a better feature set for a given task than another I2C
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IP core on the SoC. The most simple example is to fall back to GPIO bitbanging
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if your current runtime configuration hits an errata of the internal IP core.
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+-------------------------------+
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| SoC |
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| | +-----+ +-----+
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| +------------+ | | dev | | dev |
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| |I2C IP Core1|--\ | +-----+ +-----+
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| +------------+ \-------+ | | |
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| |Pinctrl|--|------+--------+
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| +------------+ +-------+ |
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| |I2C IP Core2|--/ |
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| +------------+ |
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| |
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+-------------------------------+
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Required properties:
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- compatible: "i2c-demux-pinctrl"
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- i2c-parent: List of phandles of I2C masters available for selection. The first
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one will be used as default.
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- i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C
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parents.
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Furthermore, I2C mux properties and child nodes. See i2c-mux.txt in this
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directory.
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Example:
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Here is a snipplet for a bus to be demuxed. It contains various i2c clients for
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HDMI, so the bus is named "i2c-hdmi":
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i2chdmi: i2c@8 {
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compatible = "i2c-demux-pinctrl";
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i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
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i2c-bus-name = "i2c-hdmi";
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#address-cells = <1>;
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#size-cells = <0>;
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ak4643: sound-codec@12 {
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compatible = "asahi-kasei,ak4643";
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#sound-dai-cells = <0>;
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reg = <0x12>;
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};
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composite-in@20 {
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compatible = "adi,adv7180";
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reg = <0x20>;
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remote = <&vin1>;
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port {
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adv7180: endpoint {
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bus-width = <8>;
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remote-endpoint = <&vin1ep0>;
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};
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};
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};
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hdmi@39 {
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compatible = "adi,adv7511w";
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reg = <0x39>;
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interrupt-parent = <&gpio1>;
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interrupts = <15 IRQ_TYPE_LEVEL_LOW>;
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adi,input-depth = <8>;
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adi,input-colorspace = "rgb";
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adi,input-clock = "1x";
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adi,input-style = <1>;
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adi,input-justification = "evenly";
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ports {
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#address-cells = <1>;
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#size-cells = <0>;
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port@0 {
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reg = <0>;
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adv7511_in: endpoint {
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remote-endpoint = <&du_out_lvds0>;
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};
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};
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port@1 {
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reg = <1>;
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adv7511_out: endpoint {
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remote-endpoint = <&hdmi_con>;
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};
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};
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};
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};
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};
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And for clarification, here are the snipplets for the i2c-parents:
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gpioi2c: i2c@9 {
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#address-cells = <1>;
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#size-cells = <0>;
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compatible = "i2c-gpio";
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gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */
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&gpio5 5 GPIO_ACTIVE_HIGH /* scl */
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>;
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i2c-gpio,delay-us = <5>;
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};
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...
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&i2c2 {
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pinctrl-0 = <&i2c2_pins>;
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pinctrl-names = "i2c-hdmi";
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clock-frequency = <100000>;
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};
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...
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&iic2 {
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pinctrl-0 = <&iic2_pins>;
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pinctrl-names = "i2c-hdmi";
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clock-frequency = <100000>;
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};
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Please note:
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- pinctrl properties for the parent I2C controllers need a pinctrl state
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with the same name as i2c-bus-name, not "default"!
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- the i2c masters must have their status "disabled". This driver will
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enable them at runtime when needed.
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