i2c-mux-gpmux.txt

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    1 General Purpose I2C Bus Mux
    2 
    3 This binding describes an I2C bus multiplexer that uses a mux controller
    4 from the mux subsystem to route the I2C signals.
    5 
    6                                   .-----.  .-----.
    7                                   | dev |  | dev |
    8     .------------.                '-----'  '-----'
    9     | SoC        |                   |        |
   10     |            |          .--------+--------'
   11     |   .------. |  .------+    child bus A, on MUX value set to 0
   12     |   | I2C  |-|--| Mux  |
   13     |   '------' |  '--+---+    child bus B, on MUX value set to 1
   14     |   .------. |     |    '----------+--------+--------.
   15     |   | MUX- | |     |               |        |        |
   16     |   | Ctrl |-|-----+            .-----.  .-----.  .-----.
   17     |   '------' |                  | dev |  | dev |  | dev |
   18     '------------'                  '-----'  '-----'  '-----'
   19 
   20 Required properties:
   21 - compatible: i2c-mux
   22 - i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
   23   port is connected to.
   24 - mux-controls: The phandle of the mux controller to use for operating the
   25   mux.
   26 * Standard I2C mux properties. See i2c-mux.txt in this directory.
   27 * I2C child bus nodes. See i2c-mux.txt in this directory. The sub-bus number
   28   is also the mux-controller state described in ../mux/mux-controller.txt
   29 
   30 Optional properties:
   31 - mux-locked: If present, explicitly allow unrelated I2C transactions on the
   32   parent I2C adapter at these times:
   33    + during setup of the multiplexer
   34    + between setup of the multiplexer and the child bus I2C transaction
   35    + between the child bus I2C transaction and releasing of the multiplexer
   36    + during releasing of the multiplexer
   37   However, I2C transactions to devices behind all I2C multiplexers connected
   38   to the same parent adapter that this multiplexer is connected to are blocked
   39   for the full duration of the complete multiplexed I2C transaction (i.e.
   40   including the times covered by the above list).
   41   If mux-locked is not present, the multiplexer is assumed to be parent-locked.
   42   This means that no unrelated I2C transactions are allowed on the parent I2C
   43   adapter for the complete multiplexed I2C transaction.
   44   The properties of mux-locked and parent-locked multiplexers are discussed
   45   in more detail in Documentation/i2c/i2c-topology.rst.
   46 
   47 For each i2c child node, an I2C child bus will be created. They will
   48 be numbered based on their order in the device tree.
   49 
   50 Whenever an access is made to a device on a child bus, the value set
   51 in the relevant node's reg property will be set as the state in the
   52 mux controller.
   53 
   54 Example:
   55         mux: mux-controller {
   56                 compatible = "gpio-mux";
   57                 #mux-control-cells = <0>;
   58 
   59                 mux-gpios = <&pioA 0 GPIO_ACTIVE_HIGH>,
   60                             <&pioA 1 GPIO_ACTIVE_HIGH>;
   61         };
   62 
   63         i2c-mux {
   64                 compatible = "i2c-mux";
   65                 mux-locked;
   66                 i2c-parent = <&i2c1>;
   67 
   68                 mux-controls = <&mux>;
   69 
   70                 #address-cells = <1>;
   71                 #size-cells = <0>;
   72 
   73                 i2c@1 {
   74                         reg = <1>;
   75                         #address-cells = <1>;
   76                         #size-cells = <0>;
   77 
   78                         ssd1307: oled@3c {
   79                                 compatible = "solomon,ssd1307fb-i2c";
   80                                 reg = <0x3c>;
   81                                 pwms = <&pwm 4 3000>;
   82                                 reset-gpios = <&gpio2 7 1>;
   83                                 reset-active-low;
   84                         };
   85                 };
   86 
   87                 i2c@3 {
   88                         reg = <3>;
   89                         #address-cells = <1>;
   90                         #size-cells = <0>;
   91 
   92                         pca9555: pca9555@20 {
   93                                 compatible = "nxp,pca9555";
   94                                 gpio-controller;
   95                                 #gpio-cells = <2>;
   96                                 reg = <0x20>;
   97                         };
   98                 };
   99         };

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FreeBSD/Linux Kernel Cross Reference sys/contrib/device-tree/Bindings/i2c/i2c-mux-gpmux.txt

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sys/contrib/device-tree/Bindings/i2c/i2c-mux-gpmux.txt