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80 lines
2.5 KiB
80 lines
2.5 KiB
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 i2c-mux.yaml in this directory. |
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* I2C child bus nodes. See i2c-mux.yaml 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 relevant 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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}; |
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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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