Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt

   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
  30 Furthermore, I2C mux properties and child nodes. See i2c-mux.txt in this
  31 directory.
  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.