| Tom Rini | 53633a8 | 2024-02-29 12:33:36 -0500 | [diff] [blame^] | 1 | # SPDX-License-Identifier: GPL-2.0-only |
| 2 | %YAML 1.2 |
| 3 | --- |
| 4 | $id: http://devicetree.org/schemas/i2c/i2c-mux-gpio.yaml# |
| 5 | $schema: http://devicetree.org/meta-schemas/core.yaml# |
| 6 | |
| 7 | title: GPIO-based I2C Bus Mux |
| 8 | |
| 9 | maintainers: |
| 10 | - Wolfram Sang <wsa@kernel.org> |
| 11 | |
| 12 | description: | |
| 13 | This binding describes an I2C bus multiplexer that uses GPIOs to route the I2C signals. |
| 14 | |
| 15 | +-----+ +-----+ |
| 16 | | dev | | dev | |
| 17 | +------------+ +-----+ +-----+ |
| 18 | | SoC | | | |
| 19 | | | /--------+--------+ |
| 20 | | +------+ | +------+ child bus A, on GPIO value set to 0 |
| 21 | | | I2C |-|--| Mux | |
| 22 | | +------+ | +--+---+ child bus B, on GPIO value set to 1 |
| 23 | | | | \----------+--------+--------+ |
| 24 | | +------+ | | | | | |
| 25 | | | GPIO |-|-----+ +-----+ +-----+ +-----+ |
| 26 | | +------+ | | dev | | dev | | dev | |
| 27 | +------------+ +-----+ +-----+ +-----+ |
| 28 | |
| 29 | For each I2C child node, an I2C child bus will be created. They will be numbered based on their |
| 30 | order in the device tree. |
| 31 | |
| 32 | Whenever an access is made to a device on a child bus, the value set in the relevant node's reg |
| 33 | property will be output using the list of GPIOs, the first in the list holding the least- |
| 34 | significant value. |
| 35 | |
| 36 | If an idle state is defined, using the idle-state (optional) property, whenever an access is not |
| 37 | being made to a device on a child bus, the GPIOs will be set according to the idle value. |
| 38 | |
| 39 | If an idle state is not defined, the most recently used value will be left programmed into |
| 40 | hardware whenever no access is being made to a device on a child bus. |
| 41 | |
| 42 | properties: |
| 43 | compatible: |
| 44 | const: i2c-mux-gpio |
| 45 | |
| 46 | i2c-parent: |
| 47 | description: phandle of the I2C bus that this multiplexer's master-side port is connected to |
| 48 | $ref: /schemas/types.yaml#/definitions/phandle |
| 49 | |
| 50 | mux-gpios: |
| 51 | description: list of GPIOs used to control the muxer |
| 52 | minItems: 1 |
| 53 | maxItems: 4 # Should be enough |
| 54 | |
| 55 | idle-state: |
| 56 | description: Value to set the muxer to when idle. When no value is given, it defaults to the |
| 57 | last value used. |
| 58 | $ref: /schemas/types.yaml#/definitions/uint32 |
| 59 | |
| 60 | allOf: |
| 61 | - $ref: i2c-mux.yaml |
| 62 | |
| 63 | unevaluatedProperties: false |
| 64 | |
| 65 | required: |
| 66 | - compatible |
| 67 | - i2c-parent |
| 68 | - mux-gpios |
| 69 | |
| 70 | examples: |
| 71 | - | |
| 72 | i2cmux { |
| 73 | compatible = "i2c-mux-gpio"; |
| 74 | #address-cells = <1>; |
| 75 | #size-cells = <0>; |
| 76 | mux-gpios = <&gpio1 22 0>, <&gpio1 23 0>; |
| 77 | i2c-parent = <&i2c1>; |
| 78 | |
| 79 | i2c@1 { |
| 80 | reg = <1>; |
| 81 | #address-cells = <1>; |
| 82 | #size-cells = <0>; |
| 83 | |
| 84 | ssd1307: oled@3c { |
| 85 | compatible = "solomon,ssd1307fb-i2c"; |
| 86 | reg = <0x3c>; |
| 87 | pwms = <&pwm 4 3000>; |
| 88 | reset-gpios = <&gpio2 7 1>; |
| 89 | }; |
| 90 | }; |
| 91 | |
| 92 | i2c@3 { |
| 93 | reg = <3>; |
| 94 | #address-cells = <1>; |
| 95 | #size-cells = <0>; |
| 96 | |
| 97 | pca9555: pca9555@20 { |
| 98 | compatible = "nxp,pca9555"; |
| 99 | gpio-controller; |
| 100 | #gpio-cells = <2>; |
| 101 | reg = <0x20>; |
| 102 | }; |
| 103 | }; |
| 104 | }; |