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 mux.txt in this directory.
  31
  32 Example:
  33
  34 Here is a snipplet for a bus to be demuxed. It contains various i2c clients for
  35 HDMI, so the bus is named "i2c-hdmi":
  36
  37         i2chdmi: i2c@8 {
  38
  39                 compatible = "i2c-demux-pinctrl";
  40                 i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
  41                 i2c-bus-name = "i2c-hdmi";
  42                 #address-cells = <1>;
  43                 #size-cells = <0>;
  44
  45                 ak4643: sound-codec@12 {
  46                         compatible = "asahi-kasei,ak4643";
  47
  48                         #sound-dai-cells = <0>;
  49                         reg = <0x12>;
  50                 };
  51
  52                 composite-in@20 {
  53                         compatible = "adi,adv7180";
  54                         reg = <0x20>;
  55                         remote = <&vin1>;
  56
  57                         port {
  58                                 adv7180: endpoint {
  59                                         bus-width = <8>;
  60                                         remote-endpoint = <&vin1ep0>;
  61                                 };
  62                         };
  63                 };
  64
  65                 hdmi@39 {
  66                         compatible = "adi,adv7511w";
  67                         reg = <0x39>;
  68                         interrupt-parent = <&gpio1>;
  69                         interrupts = <15 IRQ_TYPE_LEVEL_LOW>;
  70
  71                         adi,input-depth = <8>;
  72                         adi,input-colorspace = "rgb";
  73                         adi,input-clock = "1x";
  74                         adi,input-style = <1>;
  75                         adi,input-justification = "evenly";
  76
  77                         ports {
  78                                 #address-cells = <1>;
  79                                 #size-cells = <0>;
  80
  81                                 port@0 {
  82                                         reg = <0>;
  83                                         adv7511_in: endpoint {
  84                                                 remote-endpoint = <&du_out_lvds0>;
  85                                         };
  86                                 };
  87
  88                                 port@1 {
  89                                         reg = <1>;
  90                                         adv7511_out: endpoint {
  91                                                 remote-endpoint = <&hdmi_con>;
  92                                         };
  93                                 };
  94                         };
  95                 };
  96         };
  97
  98 And for clarification, here are the snipplets for the i2c-parents:
  99
 100         gpioi2c: i2c@9 {
 101                 #address-cells = <1>;
 102                 #size-cells = <0>;
 103                 compatible = "i2c-gpio";
 104                 status = "disabled";
 105                 gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */
 106                          &gpio5 5 GPIO_ACTIVE_HIGH /* scl */
 107                         >;
 108                 i2c-gpio,delay-us = <5>;
 109         };
 110
 111 ...
 112
 113 &i2c2   {
 114         pinctrl-0 = <&i2c2_pins>;
 115         pinctrl-names = "i2c-hdmi";
 116
 117         clock-frequency = <100000>;
 118 };
 119
 120 ...
 121
 122 &iic2   {
 123         pinctrl-0 = <&iic2_pins>;
 124         pinctrl-names = "i2c-hdmi";
 125
 126         clock-frequency = <100000>;
 127 };
 128
 129 Please note:
 130
 131 - pinctrl properties for the parent I2C controllers need a pinctrl state
 132   with the same name as i2c-bus-name, not "default"!
 133
 134 - the i2c masters must have their status "disabled". This driver will
 135   enable them at runtime when needed.