Wolfram Sang | 50a5ba8 | 2016-01-13 15:29:27 +0100 | [diff] [blame] | 1 | Pinctrl-based I2C Bus DeMux |
| 2 | |
| 3 | This binding describes an I2C bus demultiplexer that uses pin multiplexing to |
| 4 | route the I2C signals, and represents the pin multiplexing configuration using |
| 5 | the pinctrl device tree bindings. This may be used to select one I2C IP core at |
| 6 | runtime which may have a better feature set for a given task than another I2C |
| 7 | IP core on the SoC. The most simple example is to fall back to GPIO bitbanging |
| 8 | if your current runtime configuration hits an errata of the internal IP core. |
| 9 | |
| 10 | +-------------------------------+ |
| 11 | | SoC | |
| 12 | | | +-----+ +-----+ |
| 13 | | +------------+ | | dev | | dev | |
| 14 | | |I2C IP Core1|--\ | +-----+ +-----+ |
| 15 | | +------------+ \-------+ | | | |
| 16 | | |Pinctrl|--|------+--------+ |
| 17 | | +------------+ +-------+ | |
| 18 | | |I2C IP Core2|--/ | |
| 19 | | +------------+ | |
| 20 | | | |
| 21 | +-------------------------------+ |
| 22 | |
| 23 | Required properties: |
| 24 | - compatible: "i2c-demux-pinctrl" |
| 25 | - i2c-parent: List of phandles of I2C masters available for selection. The first |
| 26 | one will be used as default. |
| 27 | - i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C |
| 28 | parents. |
| 29 | |
Simon Horman | 2e93284 | 2016-06-08 15:21:39 +0900 | [diff] [blame] | 30 | Furthermore, I2C mux properties and child nodes. See i2c-mux.txt in this |
| 31 | directory. |
Wolfram Sang | 50a5ba8 | 2016-01-13 15:29:27 +0100 | [diff] [blame] | 32 | |
| 33 | Example: |
| 34 | |
| 35 | Here is a snipplet for a bus to be demuxed. It contains various i2c clients for |
| 36 | HDMI, so the bus is named "i2c-hdmi": |
| 37 | |
| 38 | i2chdmi: i2c@8 { |
| 39 | |
| 40 | compatible = "i2c-demux-pinctrl"; |
| 41 | i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>; |
| 42 | i2c-bus-name = "i2c-hdmi"; |
| 43 | #address-cells = <1>; |
| 44 | #size-cells = <0>; |
| 45 | |
| 46 | ak4643: sound-codec@12 { |
| 47 | compatible = "asahi-kasei,ak4643"; |
| 48 | |
| 49 | #sound-dai-cells = <0>; |
| 50 | reg = <0x12>; |
| 51 | }; |
| 52 | |
| 53 | composite-in@20 { |
| 54 | compatible = "adi,adv7180"; |
| 55 | reg = <0x20>; |
| 56 | remote = <&vin1>; |
| 57 | |
| 58 | port { |
| 59 | adv7180: endpoint { |
| 60 | bus-width = <8>; |
| 61 | remote-endpoint = <&vin1ep0>; |
| 62 | }; |
| 63 | }; |
| 64 | }; |
| 65 | |
| 66 | hdmi@39 { |
| 67 | compatible = "adi,adv7511w"; |
| 68 | reg = <0x39>; |
| 69 | interrupt-parent = <&gpio1>; |
| 70 | interrupts = <15 IRQ_TYPE_LEVEL_LOW>; |
| 71 | |
| 72 | adi,input-depth = <8>; |
| 73 | adi,input-colorspace = "rgb"; |
| 74 | adi,input-clock = "1x"; |
| 75 | adi,input-style = <1>; |
| 76 | adi,input-justification = "evenly"; |
| 77 | |
| 78 | ports { |
| 79 | #address-cells = <1>; |
| 80 | #size-cells = <0>; |
| 81 | |
| 82 | port@0 { |
| 83 | reg = <0>; |
| 84 | adv7511_in: endpoint { |
| 85 | remote-endpoint = <&du_out_lvds0>; |
| 86 | }; |
| 87 | }; |
| 88 | |
| 89 | port@1 { |
| 90 | reg = <1>; |
| 91 | adv7511_out: endpoint { |
| 92 | remote-endpoint = <&hdmi_con>; |
| 93 | }; |
| 94 | }; |
| 95 | }; |
| 96 | }; |
| 97 | }; |
| 98 | |
| 99 | And for clarification, here are the snipplets for the i2c-parents: |
| 100 | |
| 101 | gpioi2c: i2c@9 { |
| 102 | #address-cells = <1>; |
| 103 | #size-cells = <0>; |
| 104 | compatible = "i2c-gpio"; |
| 105 | status = "disabled"; |
| 106 | gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */ |
| 107 | &gpio5 5 GPIO_ACTIVE_HIGH /* scl */ |
| 108 | >; |
| 109 | i2c-gpio,delay-us = <5>; |
| 110 | }; |
| 111 | |
| 112 | ... |
| 113 | |
| 114 | &i2c2 { |
| 115 | pinctrl-0 = <&i2c2_pins>; |
| 116 | pinctrl-names = "i2c-hdmi"; |
| 117 | |
| 118 | clock-frequency = <100000>; |
| 119 | }; |
| 120 | |
| 121 | ... |
| 122 | |
| 123 | &iic2 { |
| 124 | pinctrl-0 = <&iic2_pins>; |
| 125 | pinctrl-names = "i2c-hdmi"; |
| 126 | |
| 127 | clock-frequency = <100000>; |
| 128 | }; |
| 129 | |
| 130 | Please note: |
| 131 | |
| 132 | - pinctrl properties for the parent I2C controllers need a pinctrl state |
| 133 | with the same name as i2c-bus-name, not "default"! |
| 134 | |
| 135 | - the i2c masters must have their status "disabled". This driver will |
| 136 | enable them at runtime when needed. |