diff options
Diffstat (limited to 'Documentation/devicetree')
-rw-r--r-- | Documentation/devicetree/bindings/cpu/cpu-topology.txt (renamed from Documentation/devicetree/bindings/arm/topology.txt) | 256 |
1 files changed, 167 insertions, 89 deletions
diff --git a/Documentation/devicetree/bindings/arm/topology.txt b/Documentation/devicetree/bindings/cpu/cpu-topology.txt index b0d80c0fb265..99918189403c 100644 --- a/Documentation/devicetree/bindings/arm/topology.txt +++ b/Documentation/devicetree/bindings/cpu/cpu-topology.txt @@ -1,21 +1,19 @@ =========================================== -ARM topology binding description +CPU topology binding description =========================================== =========================================== 1 - Introduction =========================================== -In an ARM system, the hierarchy of CPUs is defined through three entities that +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 cpu nodes (bindings defined in [1]) represent the devices that -correspond to physical CPUs and are to be mapped to the hierarchy levels. - The bottom hierarchy level sits at core or thread level depending on whether symmetric multi-threading (SMT) is supported or not. @@ -24,33 +22,31 @@ 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. -ARM topology bindings allow one to associate cpu nodes with hierarchical groups +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. -The remainder of this document provides the topology bindings for ARM, based -on the Devicetree Specification, available from: +Currently, only ARM/RISC-V intend to use this cpu topology binding but it may be +used for any other architecture as well. -https://www.devicetree.org/specifications/ +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. -If not stated otherwise, whenever a reference to a cpu node phandle is made its -value must point to a cpu node compliant with the cpu node bindings as -documented in [1]. A topology description containing phandles to cpu nodes that are not compliant -with bindings standardized in [1] is therefore considered invalid. +with bindings standardized in [4] is therefore considered invalid. =========================================== 2 - cpu-map node =========================================== -The ARM CPU topology is defined within the cpu-map node, which is a direct +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 ARM SMP systems provide CPUs topology to the OS. - ARM uniprocessor systems do not require a topology + 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. @@ -63,21 +59,23 @@ nodes are listed. The cpu-map node's child nodes can be: - - one or more cluster nodes + - 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 three types of child nodes: +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 (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 +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. =========================================== @@ -85,26 +83,44 @@ invalid and therefore must be ignored. =========================================== cpu-map child nodes must follow a naming convention where the node name -must be "clusterN", "coreN", "threadN" depending on the node type (ie -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 +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 - cluster/core/thread node bindings +3 - socket/cluster/core/thread node bindings =========================================== -Bindings for cluster/cpu/thread nodes are defined as follows: +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 and cluster nodes can be contained in parent - cluster nodes. + 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. @@ -164,90 +180,93 @@ Bindings for cluster/cpu/thread nodes are defined as follows: 4 - Example dts =========================================== -Example 1 (ARM 64-bit, 16-cpu system, two clusters of clusters): +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 { - cluster0 { + socket0 { cluster0 { - core0 { - thread0 { - cpu = <&CPU0>; + cluster0 { + core0 { + thread0 { + cpu = <&CPU0>; + }; + thread1 { + cpu = <&CPU1>; + }; }; - thread1 { - cpu = <&CPU1>; - }; - }; - core1 { - thread0 { - cpu = <&CPU2>; - }; - thread1 { - cpu = <&CPU3>; + core1 { + thread0 { + cpu = <&CPU2>; + }; + thread1 { + cpu = <&CPU3>; + }; }; }; - }; - cluster1 { - core0 { - thread0 { - cpu = <&CPU4>; - }; - thread1 { - cpu = <&CPU5>; + 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>; + core1 { + thread0 { + cpu = <&CPU6>; + }; + thread1 { + cpu = <&CPU7>; + }; }; }; }; cluster1 { - core0 { - thread0 { - cpu = <&CPU12>; + cluster0 { + core0 { + thread0 { + cpu = <&CPU8>; + }; + thread1 { + cpu = <&CPU9>; + }; }; - thread1 { - cpu = <&CPU13>; + core1 { + thread0 { + cpu = <&CPU10>; + }; + thread1 { + cpu = <&CPU11>; + }; }; }; - core1 { - thread0 { - cpu = <&CPU14>; + + cluster1 { + core0 { + thread0 { + cpu = <&CPU12>; + }; + thread1 { + cpu = <&CPU13>; + }; }; - thread1 { - cpu = <&CPU15>; + core1 { + thread0 { + cpu = <&CPU14>; + }; + thread1 { + cpu = <&CPU15>; + }; }; }; }; @@ -470,6 +489,65 @@ cpus { }; }; +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.txt +[4] https://www.devicetree.org/specifications/ |