[PATCH v8 05/18] dt-bindings: RISC-V CPU Bindings

Palmer Dabbelt
2017-09-12T21:57:50Z

This patch adds device tree bindings for RISC-V CPUs, patterned after
the ARM device tree CPU bindings.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
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