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-RISC-V Hart-Level Interrupt Controller (HLIC)
----------------------------------------------
-
-RISC-V cores include Control Status Registers (CSRs) which are local to each
-CPU core (HART in RISC-V terminology) and can be read or written by software.
-Some of these CSRs are used to control local interrupts connected to the core.
-Every interrupt is ultimately routed through a hart's HLIC before it
-interrupts that hart.
-
-The RISC-V supervisor ISA manual specifies three interrupt sources that are
-attached to every HLIC: software interrupts, the timer interrupt, and external
-interrupts. Software interrupts are used to send IPIs between cores. The
-timer interrupt comes from an architecturally mandated real-time timer that is
-controlled via Supervisor Binary Interface (SBI) calls and CSR reads. External
-interrupts connect all other device interrupts to the HLIC, which are routed
-via the platform-level interrupt controller (PLIC).
-
-All RISC-V systems that conform to the supervisor ISA specification are
-required to have a HLIC with these three interrupt sources present. Since the
-interrupt map is defined by the ISA it's not listed in the HLIC's device tree
-entry, though external interrupt controllers (like the PLIC, for example) will
-need to define how their interrupts map to the relevant HLICs. This means
-a PLIC interrupt property will typically list the HLICs for all present HARTs
-in the system.
-
-Required properties:
-- compatible : "riscv,cpu-intc"
-- #interrupt-cells : should be <1>. The interrupt sources are defined by the
- RISC-V supervisor ISA manual, with only the following three interrupts being
- defined for supervisor mode:
- - Source 1 is the supervisor software interrupt, which can be sent by an SBI
- call and is reserved for use by software.
- - Source 5 is the supervisor timer interrupt, which can be configured by
- SBI calls and implements a one-shot timer.
- - Source 9 is the supervisor external interrupt, which chains to all other
- device interrupts.
-- interrupt-controller : Identifies the node as an interrupt controller
-
-Furthermore, this interrupt-controller MUST be embedded inside the cpu
-definition of the hart whose CSRs control these local interrupts.
-
-An example device tree entry for a HLIC is show below.
-
- cpu1: cpu@1 {
- compatible = "riscv";
- ...
- cpu1-intc: interrupt-controller {
- #interrupt-cells = <1>;
- compatible = "sifive,fu540-c000-cpu-intc", "riscv,cpu-intc";
- interrupt-controller;
- };
- };