This patch adds device tree bindings for RISC-V CPUs, patterned after the ARM device tree CPU bindings. Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxx> --- Documentation/devicetree/bindings/riscv/cpus.txt | 162 +++++++++++++++++++++++ 1 file changed, 162 insertions(+) create mode 100644 Documentation/devicetree/bindings/riscv/cpus.txt diff --git a/Documentation/devicetree/bindings/riscv/cpus.txt b/Documentation/devicetree/bindings/riscv/cpus.txt new file mode 100644 index 000000000000..adf7b7af5dc3 --- /dev/null +++ b/Documentation/devicetree/bindings/riscv/cpus.txt @@ -0,0 +1,162 @@ +=================== +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"; + } + } + } -- 2.13.5 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
