FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/interrupt-controller/st,spear3xx-shirq.txt

     * SPEAr Shared IRQ layer (shirq)
     
     SPEAr3xx architecture includes shared/multiplexed irqs for certain set
     of devices. The multiplexor provides a single interrupt to parent
     interrupt controller (VIC) on behalf of a group of devices.
     
     There can be multiple groups available on SPEAr3xx variants but not
     exceeding 4. The number of devices in a group can differ, further they
     may share same set of status/mask registers spanning across different
    bit masks. Also in some cases the group may not have enable or other
    registers. This makes software little complex.
    
    A single node in the device tree is used to describe the shared
    interrupt multiplexor (one node for all groups). A group in the
    interrupt controller shares config/control registers with other groups.
    For example, a 32-bit interrupt enable/disable config register can
    accommodate up to 4 interrupt groups.
    
    Required properties:
      - compatible: should be, either of
         - "st,spear300-shirq"
         - "st,spear310-shirq"
         - "st,spear320-shirq"
      - interrupt-controller: Identifies the node as an interrupt controller.
      - #interrupt-cells: should be <1> which basically contains the offset
        (starting from 0) of interrupts for all the groups.
      - reg: Base address and size of shirq registers.
      - interrupts: The list of interrupts generated by the groups which are
        then connected to a parent interrupt controller. Each group is
        associated with one of the interrupts, hence number of interrupts (to
        parent) is equal to number of groups. The format of the interrupt
        specifier depends in the interrupt parent controller.
    
    Example:
    
    The following is an example from the SPEAr320 SoC dtsi file.
    
    shirq: interrupt-controller@b3000000 {
            compatible = "st,spear320-shirq";
            reg = <0xb3000000 0x1000>;
            interrupts = <28 29 30 1>;
            #interrupt-cells = <1>;
            interrupt-controller;
    };

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