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* ARC-HS Interrupt Distribution Unit

  This optional 2nd level interrupt controller can be used in SMP configurations for
  dynamic IRQ routing, load balancing of common/external IRQs towards core intc.

Properties:

- compatible: "snps,archs-idu-intc"
- interrupt-controller: This is an interrupt controller.
- interrupt-parent: <reference to parent core intc>
- #interrupt-cells: Must be <2>.
- interrupts: <...> specifies the upstream core irqs

  First cell specifies the "common" IRQ from peripheral to IDU
  Second cell specifies the irq distribution mode to cores
     0=Round Robin; 1=cpu0, 2=cpu1, 4=cpu2, 8=cpu3

  intc accessed via the special ARC AUX register interface, hence "reg" property
  is not specified.

Example:
	core_intc: core-interrupt-controller {
		compatible = "snps,archs-intc";
		interrupt-controller;
		#interrupt-cells = <1>;
	};

	idu_intc: idu-interrupt-controller {
		compatible = "snps,archs-idu-intc";
		interrupt-controller;
		interrupt-parent = <&core_intc>;

		/*
		 * <hwirq  distribution>
		 * distribution: 0=RR; 1=cpu0, 2=cpu1, 4=cpu2, 8=cpu3
		 */
		#interrupt-cells = <2>;

		/* upstream core irqs: downstream these are "COMMON" irq 0,1..  */
		interrupts = <24 25 26 27 28 29 30 31>;
	};

	some_device: serial@c0fc1000 {
		interrupt-parent = <&idu_intc>;
		interrupts = <0 0>;	/* upstream idu IRQ #24, Round Robin */
	};