FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/i3c/i3c.txt

     Generic device tree bindings for I3C busses
     ===========================================
     
     This document describes generic bindings that should be used to describe I3C
     busses in a device tree.
     
     Required properties
     -------------------
     
    - #address-cells  - should be <3>. Read more about addresses below.
    - #size-cells     - should be <0>.
    - compatible      - name of the I3C master controller driving the I3C bus
    
    For other required properties e.g. to describe register sets,
    clocks, etc. check the binding documentation of the specific driver.
    The node describing an I3C bus should be named i3c-master.
    
    Optional properties
    -------------------
    
    These properties may not be supported by all I3C master drivers. Each I3C
    master bindings should specify which of them are supported.
    
    - i3c-scl-hz: frequency of the SCL signal used for I3C transfers.
                  When undefined the core sets it to 12.5MHz.
    
    - i2c-scl-hz: frequency of the SCL signal used for I2C transfers.
                  When undefined, the core looks at LVR (Legacy Virtual Register)
                  values of I2C devices described in the device tree to determine
                  the maximum I2C frequency.
    
    I2C devices
    ===========
    
    Each I2C device connected to the bus should be described in a subnode. All
    properties described in Documentation/devicetree/bindings/i2c/i2c.txt are
    valid here, but several new properties have been added.
    
    New constraint on existing properties:
    --------------------------------------
    - reg: contains 3 cells
      + first cell : still encoding the I2C address. 10 bit addressing is not
        supported. Devices with 10 bit address can't be properly passed through
        DEFSLVS command.
    
      + second cell: shall be 0
    
      + third cell: shall encode the I3C LVR (Legacy Virtual Register)
            bit[31:8]: unused/ignored
            bit[7:5]: I2C device index. Possible values
            * 0: I2C device has a 50 ns spike filter
            * 1: I2C device does not have a 50 ns spike filter but supports high
                 frequency on SCL
            * 2: I2C device does not have a 50 ns spike filter and is not tolerant
                 to high frequencies
            * 3-7: reserved
    
            bit[4]: tell whether the device operates in FM (Fast Mode) or FM+ mode
            * 0: FM+ mode
            * 1: FM mode
    
            bit[3:0]: device type
            * 0-15: reserved
    
    The I2C node unit-address should always match the first cell of the reg
    property: <device-type>@<i2c-address>.
    
    I3C devices
    ===========
    
    All I3C devices are supposed to support DAA (Dynamic Address Assignment), and
    are thus discoverable. So, by default, I3C devices do not have to be described
    in the device tree.
    This being said, one might want to attach extra resources to these devices,
    and those resources may have to be described in the device tree, which in turn
    means we have to describe I3C devices.
    
    Another use case for describing an I3C device in the device tree is when this
    I3C device has a static I2C address and we want to assign it a specific I3C
    dynamic address before the DAA takes place (so that other devices on the bus
    can't take this dynamic address).
    
    The I3C device should be names <device-type>@<static-i2c-address>,<i3c-pid>,
    where device-type is describing the type of device connected on the bus
    (gpio-controller, sensor, ...).
    
    Required properties
    -------------------
    - reg: contains 3 cells
      + first cell : encodes the static I2C address. Should be 0 if the device does
                     not have one (0 is not a valid I2C address).
    
      + second and third cells: should encode the ProvisionalID. The second cell
                                contains the manufacturer ID left-shifted by 1.
                                The third cell contains ORing of the part ID
                                left-shifted by 16, the instance ID left-shifted
                                by 12 and the extra information. This encoding is
                                following the PID definition provided by the I3C
                                specification.
   
   Optional properties
   -------------------
   - assigned-address: dynamic address to be assigned to this device. This
                       property is only valid if the I3C device has a static
                       address (first cell of the reg property != 0).
   
   
   Example:
   
           i3c-master@d040000 {
                   compatible = "cdns,i3c-master";
                   clocks = <&coreclock>, <&i3csysclock>;
                   clock-names = "pclk", "sysclk";
                   interrupts = <3 0>;
                   reg = <0x0d040000 0x1000>;
                   #address-cells = <3>;
                   #size-cells = <0>;
                   i2c-scl-hz = <100000>;
   
                   /* I2C device. */
                   nunchuk: nunchuk@52 {
                           compatible = "nintendo,nunchuk";
                           reg = <0x52 0x0 0x10>;
                   };
   
                   /* I3C device with a static I2C address. */
                   thermal_sensor: sensor@68,39200144004 {
                           reg = <0x68 0x392 0x144004>;
                           assigned-address = <0xa>;
                   };
   
                   /*
                    * I3C device without a static I2C address but requiring
                    * resources described in the DT.
                    */
                   sensor@0,39200154004 {
                           reg = <0x0 0x392 0x154004>;
                           clocks = <&clock_provider 0>;
                   };
           };

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