+++ /dev/null
-===========================================
-CPU topology binding description
-===========================================
-
-===========================================
-1 - Introduction
-===========================================
-
-In a SMP system, the hierarchy of CPUs is defined through three entities that
-are used to describe the layout of physical CPUs in the system:
-
-- socket
-- cluster
-- core
-- thread
-
-The bottom hierarchy level sits at core or thread level depending on whether
-symmetric multi-threading (SMT) is supported or not.
-
-For instance in a system where CPUs support SMT, "cpu" nodes represent all
-threads existing in the system and map to the hierarchy level "thread" above.
-In systems where SMT is not supported "cpu" nodes represent all cores present
-in the system and map to the hierarchy level "core" above.
-
-CPU topology bindings allow one to associate cpu nodes with hierarchical groups
-corresponding to the system hierarchy; syntactically they are defined as device
-tree nodes.
-
-Currently, only ARM/RISC-V intend to use this cpu topology binding but it may be
-used for any other architecture as well.
-
-The cpu nodes, as per bindings defined in [4], represent the devices that
-correspond to physical CPUs and are to be mapped to the hierarchy levels.
-
-A topology description containing phandles to cpu nodes that are not compliant
-with bindings standardized in [4] is therefore considered invalid.
-
-===========================================
-2 - cpu-map node
-===========================================
-
-The ARM/RISC-V CPU topology is defined within the cpu-map node, which is a direct
-child of the cpus node and provides a container where the actual topology
-nodes are listed.
-
-- cpu-map node
-
- Usage: Optional - On SMP systems provide CPUs topology to the OS.
- Uniprocessor systems do not require a topology
- description and therefore should not define a
- cpu-map node.
-
- Description: The cpu-map node is just a container node where its
- subnodes describe the CPU topology.
-
- Node name must be "cpu-map".
-
- The cpu-map node's parent node must be the cpus node.
-
- The cpu-map node's child nodes can be:
-
- - one or more cluster nodes or
- - one or more socket nodes in a multi-socket system
-
- Any other configuration is considered invalid.
-
-The cpu-map node can only contain 4 types of child nodes:
-
-- socket node
-- cluster node
-- core node
-- thread node
-
-whose bindings are described in paragraph 3.
-
-The nodes describing the CPU topology (socket/cluster/core/thread) can
-only be defined within the cpu-map node and every core/thread in the
-system must be defined within the topology. Any other configuration is
-invalid and therefore must be ignored.
-
-===========================================
-2.1 - cpu-map child nodes naming convention
-===========================================
-
-cpu-map child nodes must follow a naming convention where the node name
-must be "socketN", "clusterN", "coreN", "threadN" depending on the node type
-(ie socket/cluster/core/thread) (where N = {0, 1, ...} is the node number; nodes
-which are siblings within a single common parent node must be given a unique and
-sequential N value, starting from 0).
-cpu-map child nodes which do not share a common parent node can have the same
-name (ie same number N as other cpu-map child nodes at different device tree
-levels) since name uniqueness will be guaranteed by the device tree hierarchy.
-
-===========================================
-3 - socket/cluster/core/thread node bindings
-===========================================
-
-Bindings for socket/cluster/cpu/thread nodes are defined as follows:
-
-- socket node
-
- Description: must be declared within a cpu-map node, one node
- per physical socket in the system. A system can
- contain single or multiple physical socket.
- The association of sockets and NUMA nodes is beyond
- the scope of this bindings, please refer [2] for
- NUMA bindings.
-
- This node is optional for a single socket system.
-
- The socket node name must be "socketN" as described in 2.1 above.
- A socket node can not be a leaf node.
-
- A socket node's child nodes must be one or more cluster nodes.
-
- Any other configuration is considered invalid.
-
-- cluster node
-
- Description: must be declared within a cpu-map node, one node
- per cluster. A system can contain several layers of
- clustering within a single physical socket and cluster
- nodes can be contained in parent cluster nodes.
-
- The cluster node name must be "clusterN" as described in 2.1 above.
- A cluster node can not be a leaf node.
-
- A cluster node's child nodes must be:
-
- - one or more cluster nodes; or
- - one or more core nodes
-
- Any other configuration is considered invalid.
-
-- core node
-
- Description: must be declared in a cluster node, one node per core in
- the cluster. If the system does not support SMT, core
- nodes are leaf nodes, otherwise they become containers of
- thread nodes.
-
- The core node name must be "coreN" as described in 2.1 above.
-
- A core node must be a leaf node if SMT is not supported.
-
- Properties for core nodes that are leaf nodes:
-
- - cpu
- Usage: required
- Value type: <phandle>
- Definition: a phandle to the cpu node that corresponds to the
- core node.
-
- If a core node is not a leaf node (CPUs supporting SMT) a core node's
- child nodes can be:
-
- - one or more thread nodes
-
- Any other configuration is considered invalid.
-
-- thread node
-
- Description: must be declared in a core node, one node per thread
- in the core if the system supports SMT. Thread nodes are
- always leaf nodes in the device tree.
-
- The thread node name must be "threadN" as described in 2.1 above.
-
- A thread node must be a leaf node.
-
- A thread node must contain the following property:
-
- - cpu
- Usage: required
- Value type: <phandle>
- Definition: a phandle to the cpu node that corresponds to
- the thread node.
-
-===========================================
-4 - Example dts
-===========================================
-
-Example 1 (ARM 64-bit, 16-cpu system, two clusters of clusters in a single
-physical socket):
-
-cpus {
- #size-cells = <0>;
- #address-cells = <2>;
-
- cpu-map {
- socket0 {
- cluster0 {
- cluster0 {
- core0 {
- thread0 {
- cpu = <&CPU0>;
- };
- thread1 {
- cpu = <&CPU1>;
- };
- };
-
- core1 {
- thread0 {
- cpu = <&CPU2>;
- };
- thread1 {
- cpu = <&CPU3>;
- };
- };
- };
-
- cluster1 {
- core0 {
- thread0 {
- cpu = <&CPU4>;
- };
- thread1 {
- cpu = <&CPU5>;
- };
- };
-
- core1 {
- thread0 {
- cpu = <&CPU6>;
- };
- thread1 {
- cpu = <&CPU7>;
- };
- };
- };
- };
-
- cluster1 {
- cluster0 {
- core0 {
- thread0 {
- cpu = <&CPU8>;
- };
- thread1 {
- cpu = <&CPU9>;
- };
- };
- core1 {
- thread0 {
- cpu = <&CPU10>;
- };
- thread1 {
- cpu = <&CPU11>;
- };
- };
- };
-
- cluster1 {
- core0 {
- thread0 {
- cpu = <&CPU12>;
- };
- thread1 {
- cpu = <&CPU13>;
- };
- };
- core1 {
- thread0 {
- cpu = <&CPU14>;
- };
- thread1 {
- cpu = <&CPU15>;
- };
- };
- };
- };
- };
- };
-
- CPU0: cpu@0 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x0>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU1: cpu@1 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x1>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU2: cpu@100 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x100>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU3: cpu@101 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x101>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU4: cpu@10000 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x10000>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU5: cpu@10001 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x10001>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU6: cpu@10100 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x10100>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU7: cpu@10101 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x0 0x10101>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU8: cpu@100000000 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x0>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU9: cpu@100000001 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x1>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU10: cpu@100000100 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x100>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU11: cpu@100000101 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x101>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU12: cpu@100010000 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x10000>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU13: cpu@100010001 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x10001>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU14: cpu@100010100 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x10100>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-
- CPU15: cpu@100010101 {
- device_type = "cpu";
- compatible = "arm,cortex-a57";
- reg = <0x1 0x10101>;
- enable-method = "spin-table";
- cpu-release-addr = <0 0x20000000>;
- };
-};
-
-Example 2 (ARM 32-bit, dual-cluster, 8-cpu system, no SMT):
-
-cpus {
- #size-cells = <0>;
- #address-cells = <1>;
-
- cpu-map {
- cluster0 {
- core0 {
- cpu = <&CPU0>;
- };
- core1 {
- cpu = <&CPU1>;
- };
- core2 {
- cpu = <&CPU2>;
- };
- core3 {
- cpu = <&CPU3>;
- };
- };
-
- cluster1 {
- core0 {
- cpu = <&CPU4>;
- };
- core1 {
- cpu = <&CPU5>;
- };
- core2 {
- cpu = <&CPU6>;
- };
- core3 {
- cpu = <&CPU7>;
- };
- };
- };
-
- CPU0: cpu@0 {
- device_type = "cpu";
- compatible = "arm,cortex-a15";
- reg = <0x0>;
- };
-
- CPU1: cpu@1 {
- device_type = "cpu";
- compatible = "arm,cortex-a15";
- reg = <0x1>;
- };
-
- CPU2: cpu@2 {
- device_type = "cpu";
- compatible = "arm,cortex-a15";
- reg = <0x2>;
- };
-
- CPU3: cpu@3 {
- device_type = "cpu";
- compatible = "arm,cortex-a15";
- reg = <0x3>;
- };
-
- CPU4: cpu@100 {
- device_type = "cpu";
- compatible = "arm,cortex-a7";
- reg = <0x100>;
- };
-
- CPU5: cpu@101 {
- device_type = "cpu";
- compatible = "arm,cortex-a7";
- reg = <0x101>;
- };
-
- CPU6: cpu@102 {
- device_type = "cpu";
- compatible = "arm,cortex-a7";
- reg = <0x102>;
- };
-
- CPU7: cpu@103 {
- device_type = "cpu";
- compatible = "arm,cortex-a7";
- reg = <0x103>;
- };
-};
-
-Example 3: HiFive Unleashed (RISC-V 64 bit, 4 core system)
-
-{
- #address-cells = <2>;
- #size-cells = <2>;
- compatible = "sifive,fu540g", "sifive,fu500";
- model = "sifive,hifive-unleashed-a00";
-
- ...
- cpus {
- #address-cells = <1>;
- #size-cells = <0>;
- cpu-map {
- socket0 {
- cluster0 {
- core0 {
- cpu = <&CPU1>;
- };
- core1 {
- cpu = <&CPU2>;
- };
- core2 {
- cpu0 = <&CPU2>;
- };
- core3 {
- cpu0 = <&CPU3>;
- };
- };
- };
- };
-
- CPU1: cpu@1 {
- device_type = "cpu";
- compatible = "sifive,rocket0", "riscv";
- reg = <0x1>;
- }
-
- CPU2: cpu@2 {
- device_type = "cpu";
- compatible = "sifive,rocket0", "riscv";
- reg = <0x2>;
- }
- CPU3: cpu@3 {
- device_type = "cpu";
- compatible = "sifive,rocket0", "riscv";
- reg = <0x3>;
- }
- CPU4: cpu@4 {
- device_type = "cpu";
- compatible = "sifive,rocket0", "riscv";
- reg = <0x4>;
- }
- }
-};
-===============================================================================
-[1] ARM Linux kernel documentation
- Documentation/devicetree/bindings/arm/cpus.yaml
-[2] Devicetree NUMA binding description
- Documentation/devicetree/bindings/numa.txt
-[3] RISC-V Linux kernel documentation
- Documentation/devicetree/bindings/riscv/cpus.yaml
-[4] https://www.devicetree.org/specifications/
projects / linux-2.6-microblaze.git / commitdiff