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SiFive Platform-Level Interrupt Controller (PLIC)
-------------------------------------------------
SiFive SOCs include an implementation of the Platform-Level Interrupt Controller
(PLIC) high-level specification in the RISC-V Privileged Architecture
specification. The PLIC connects all external interrupts in the system to all
hart contexts in the system, via the external interrupt source in each hart.
A hart context is a privilege mode in a hardware execution thread. For example,
in an 4 core system with 2-way SMT, you have 8 harts and probably at least two
privilege modes per hart; machine mode and supervisor mode.
Each interrupt can be enabled on per-context basis. Any context can claim
a pending enabled interrupt and then release it once it has been handled.
Each interrupt has a configurable priority. Higher priority interrupts are
serviced first. Each context can specify a priority threshold. Interrupts
with priority below this threshold will not cause the PLIC to raise its
interrupt line leading to the context.
While the PLIC supports both edge-triggered and level-triggered interrupts,
interrupt handlers are oblivious to this distinction and therefore it is not
specified in the PLIC device-tree binding.
While the RISC-V ISA doesn't specify a memory layout for the PLIC, the
"sifive,plic-1.0.0" device is a concrete implementation of the PLIC that
contains a specific memory layout, which is documented in chapter 8 of the
SiFive U5 Coreplex Series Manual <https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf>.
Required properties:
- compatible : "sifive,plic-1.0.0" and a string identifying the actual
detailed implementation in case that specific bugs need to be worked around.
- #address-cells : should be <0> or more.
- #interrupt-cells : should be <1> or more.
- interrupt-controller : Identifies the node as an interrupt controller.
- reg : Should contain 1 register range (address and length).
- interrupts-extended : Specifies which contexts are connected to the PLIC,
with "-1" specifying that a context is not present. Each node pointed
to should be a riscv,cpu-intc node, which has a riscv node as parent.
- riscv,ndev: Specifies how many external interrupts are supported by
this controller.
Example:
plic: interrupt-controller@c000000 {
#address-cells = <0>;
#interrupt-cells = <1>;
compatible = "sifive,plic-1.0.0", "sifive,fu540-c000-plic";
interrupt-controller;
interrupts-extended = <
&cpu0-intc 11
&cpu1-intc 11 &cpu1-intc 9
&cpu2-intc 11 &cpu2-intc 9
&cpu3-intc 11 &cpu3-intc 9
&cpu4-intc 11 &cpu4-intc 9>;
reg = <0xc000000 0x4000000>;
riscv,ndev = <10>;
};
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