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81 lines
2.5 KiB
Text
81 lines
2.5 KiB
Text
GPIO-based I2C Bus Mux
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This binding describes an I2C bus multiplexer that uses GPIOs to
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route the I2C signals.
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+-----+ +-----+
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| dev | | dev |
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+------------+ +-----+ +-----+
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| SoC | | |
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| | /--------+--------+
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| +------+ | +------+ child bus A, on GPIO value set to 0
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| | I2C |-|--| Mux |
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| +------+ | +--+---+ child bus B, on GPIO value set to 1
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| | | \----------+--------+--------+
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| +------+ | | | | |
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| | GPIO |-|-----+ +-----+ +-----+ +-----+
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| +------+ | | dev | | dev | | dev |
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+------------+ +-----+ +-----+ +-----+
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Required properties:
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- compatible: i2c-mux-gpio
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- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
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port is connected to.
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- mux-gpios: list of gpios used to control the muxer
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* Standard I2C mux properties. See mux.txt in this directory.
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* I2C child bus nodes. See mux.txt in this directory.
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Optional properties:
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- idle-state: value to set the muxer to when idle. When no value is
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given, it defaults to the last value used.
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For each i2c child node, an I2C child bus will be created. They will
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be numbered based on their order in the device tree.
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Whenever an access is made to a device on a child bus, the value set
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in the revelant node's reg property will be output using the list of
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GPIOs, the first in the list holding the least-significant value.
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If an idle state is defined, using the idle-state (optional) property,
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whenever an access is not being made to a device on a child bus, the
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GPIOs will be set according to the idle value.
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If an idle state is not defined, the most recently used value will be
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left programmed into hardware whenever no access is being made to a
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device on a child bus.
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Example:
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i2cmux {
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compatible = "i2c-mux-gpio";
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#address-cells = <1>;
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#size-cells = <0>;
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mux-gpios = <&gpio1 22 0 &gpio1 23 0>;
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i2c-parent = <&i2c1>;
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i2c@1 {
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reg = <1>;
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#address-cells = <1>;
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#size-cells = <0>;
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ssd1307: oled@3c {
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compatible = "solomon,ssd1307fb-i2c";
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reg = <0x3c>;
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pwms = <&pwm 4 3000>;
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reset-gpios = <&gpio2 7 1>;
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reset-active-low;
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};
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};
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i2c@3 {
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reg = <3>;
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#address-cells = <1>;
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#size-cells = <0>;
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pca9555: pca9555@20 {
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compatible = "nxp,pca9555";
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gpio-controller;
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#gpio-cells = <2>;
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reg = <0x20>;
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};
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};
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};
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