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-===================
-RISC-V CPU Bindings
-===================
-
-The device tree allows to describe the layout of CPUs in a system through
-the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
-defining properties for every cpu.
-
-Bindings for CPU nodes follow the Devicetree Specification, available from:
-
-https://www.devicetree.org/specifications/
-
-with updates for 32-bit and 64-bit RISC-V systems provided in this document.
-
-===========
-Terminology
-===========
-
-This document uses some terminology common to the RISC-V community that is not
-widely used, the definitions of which are listed here:
-
-* hart: A hardware execution context, which contains all the state mandated by
- the RISC-V ISA: a PC and some registers. This terminology is designed to
- disambiguate software's view of execution contexts from any particular
- microarchitectural implementation strategy. For example, my Intel laptop is
- described as having one socket with two cores, each of which has two hyper
- threads. Therefore this system has four harts.
-
-=====================================
-cpus and cpu node bindings definition
-=====================================
-
-The RISC-V architecture, in accordance with the Devicetree Specification,
-requires the cpus and cpu nodes to be present and contain the properties
-described below.
-
-- cpus node
-
- Description: Container of cpu nodes
-
- The node name must be "cpus".
-
- A cpus node must define the following properties:
-
- - #address-cells
- Usage: required
- Value type: <u32>
- Definition: must be set to 1
- - #size-cells
- Usage: required
- Value type: <u32>
- Definition: must be set to 0
-
-- cpu node
-
- Description: Describes a hart context
-
- PROPERTIES
-
- - device_type
- Usage: required
- Value type: <string>
- Definition: must be "cpu"
- - reg
- Usage: required
- Value type: <u32>
- Definition: The hart ID of this CPU node
- - compatible:
- Usage: required
- Value type: <stringlist>
- Definition: must contain "riscv", may contain one of
- "sifive,rocket0"
- - mmu-type:
- Usage: optional
- Value type: <string>
- Definition: Specifies the CPU's MMU type. Possible values are
- "riscv,sv32"
- "riscv,sv39"
- "riscv,sv48"
- - riscv,isa:
- Usage: required
- Value type: <string>
- Definition: Contains the RISC-V ISA string of this hart. These
- ISA strings are defined by the RISC-V ISA manual.
-
-Example: SiFive Freedom U540G Development Kit
----------------------------------------------
-
-This system contains two harts: a hart marked as disabled that's used for
-low-level system tasks and should be ignored by Linux, and a second hart that
-Linux is allowed to run on.
-
- cpus {
- #address-cells = <1>;
- #size-cells = <0>;
- timebase-frequency = <1000000>;
- cpu@0 {
- clock-frequency = <1600000000>;
- compatible = "sifive,rocket0", "riscv";
- device_type = "cpu";
- i-cache-block-size = <64>;
- i-cache-sets = <128>;
- i-cache-size = <16384>;
- next-level-cache = <&L15 &L0>;
- reg = <0>;
- riscv,isa = "rv64imac";
- status = "disabled";
- L10: interrupt-controller {
- #interrupt-cells = <1>;
- compatible = "riscv,cpu-intc";
- interrupt-controller;
- };
- };
- cpu@1 {
- clock-frequency = <1600000000>;
- compatible = "sifive,rocket0", "riscv";
- d-cache-block-size = <64>;
- d-cache-sets = <64>;
- d-cache-size = <32768>;
- d-tlb-sets = <1>;
- d-tlb-size = <32>;
- device_type = "cpu";
- i-cache-block-size = <64>;
- i-cache-sets = <64>;
- i-cache-size = <32768>;
- i-tlb-sets = <1>;
- i-tlb-size = <32>;
- mmu-type = "riscv,sv39";
- next-level-cache = <&L15 &L0>;
- reg = <1>;
- riscv,isa = "rv64imafdc";
- status = "okay";
- tlb-split;
- L13: interrupt-controller {
- #interrupt-cells = <1>;
- compatible = "riscv,cpu-intc";
- interrupt-controller;
- };
- };
- };
-
-Example: Spike ISA Simulator with 1 Hart
-----------------------------------------
-
-This device tree matches the Spike ISA golden model as run with `spike -p1`.
-
- cpus {
- cpu@0 {
- device_type = "cpu";
- reg = <0x00000000>;
- status = "okay";
- compatible = "riscv";
- riscv,isa = "rv64imafdc";
- mmu-type = "riscv,sv48";
- clock-frequency = <0x3b9aca00>;
- interrupt-controller {
- #interrupt-cells = <0x00000001>;
- interrupt-controller;
- compatible = "riscv,cpu-intc";
- }
- }
- }