108 lines
3.2 KiB
YAML
108 lines
3.2 KiB
YAML
# SPDX-License-Identifier: GPL-2.0-only
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/i2c/i2c-mux-gpio.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: GPIO-based I2C Bus Mux
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maintainers:
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- Wolfram Sang <wsa@kernel.org>
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description: |
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This binding describes an I2C bus multiplexer that uses GPIOs to 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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For each I2C child node, an I2C child bus will be created. They will be numbered based on their
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order in the device tree.
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Whenever an access is made to a device on a child bus, the value set in the relevant node's reg
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property will be output using the list of GPIOs, the first in the list holding the least-
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significant value.
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If an idle state is defined, using the idle-state (optional) property, whenever an access is not
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being made to a device on a child bus, the 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 left programmed into
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hardware whenever no access is being made to a device on a child bus.
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properties:
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compatible:
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const: i2c-mux-gpio
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i2c-parent:
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description: phandle of the I2C bus that this multiplexer's master-side port is connected to
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$ref: /schemas/types.yaml#/definitions/phandle
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mux-gpios:
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description: list of GPIOs used to control the muxer
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minItems: 1
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maxItems: 4 # Should be enough
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idle-state:
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description: Value to set the muxer to when idle. When no value is given, it defaults to the
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last value used.
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$ref: /schemas/types.yaml#/definitions/uint32
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settle-time-us:
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description: Delay to wait before doing any transfer when a new bus gets selected.
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allOf:
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- $ref: i2c-mux.yaml
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unevaluatedProperties: false
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required:
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- compatible
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- i2c-parent
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- mux-gpios
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examples:
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- |
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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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