FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/spi/spi-sprd-adi.txt

     Spreadtrum ADI controller
     
     ADI is the abbreviation of Anolog-Digital interface, which is used to access
     analog chip (such as PMIC) from digital chip. ADI controller follows the SPI
     framework for its hardware implementation is alike to SPI bus and its timing
     is compatile to SPI timing.
     
     ADI controller has 50 channels including 2 software read/write channels and
     48 hardware channels to access analog chip. For 2 software read/write channels,
    users should set ADI registers to access analog chip. For hardware channels,
    we can configure them to allow other hardware components to use it independently,
    which means we can just link one analog chip address to one hardware channel,
    then users can access the mapped analog chip address by this hardware channel
    triggered by hardware components instead of ADI software channels.
    
    Thus we introduce one property named "sprd,hw-channels" to configure hardware
    channels, the first value specifies the hardware channel id which is used to
    transfer data triggered by hardware automatically, and the second value specifies
    the analog chip address where user want to access by hardware components.
    
    Since we have multi-subsystems will use unique ADI to access analog chip, when
    one system is reading/writing data by ADI software channels, that should be under
    one hardware spinlock protection to prevent other systems from reading/writing
    data by ADI software channels at the same time, or two parallel routine of setting
    ADI registers will make ADI controller registers chaos to lead incorrect results.
    Then we need one hardware spinlock to synchronize between the multiple subsystems.
    
    The new version ADI controller supplies multiple master channels for different
    subsystem accessing, that means no need to add hardware spinlock to synchronize,
    thus change the hardware spinlock support to be optional to keep backward
    compatibility.
    
    Required properties:
    - compatible: Should be "sprd,sc9860-adi".
    - reg: Offset and length of ADI-SPI controller register space.
    - #address-cells: Number of cells required to define a chip select address
            on the ADI-SPI bus. Should be set to 1.
    - #size-cells: Size of cells required to define a chip select address size
            on the ADI-SPI bus. Should be set to 0.
    
    Optional properties:
    - hwlocks: Reference to a phandle of a hwlock provider node.
    - hwlock-names: Reference to hwlock name strings defined in the same order
            as the hwlocks, should be "adi".
    - sprd,hw-channels: This is an array of channel values up to 49 channels.
            The first value specifies the hardware channel id which is used to
            transfer data triggered by hardware automatically, and the second
            value specifies the analog chip address where user want to access
            by hardware components.
    
    SPI slave nodes must be children of the SPI controller node and can contain
    properties described in Documentation/devicetree/bindings/spi/spi-bus.txt.
    
    Example:
            adi_bus: spi@40030000 {
                    compatible = "sprd,sc9860-adi";
                    reg = <0 0x40030000 0 0x10000>;
                    hwlocks = <&hwlock1 0>;
                    hwlock-names = "adi";
                    #address-cells = <1>;
                    #size-cells = <0>;
                    sprd,hw-channels = <30 0x8c20>;
            };

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