================= ARM CPUs 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 ePAPR v1.1 standard, available from: https://www.power.org/documentation/epapr-version-1-1/ with updates for 32-bit and 64-bit ARM systems provided in this document. ================================ Convention used in this document ================================ This document follows the conventions described in the ePAPR v1.1, with the addition: - square brackets define bitfields, eg reg[7:0] value of the bitfield in the reg property contained in bits 7 down to 0 ===================================== cpus and cpu node bindings definition ===================================== The ARM architecture, in accordance with the ePAPR, 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: Definition depends on ARM architecture version and configuration: # On uniprocessor ARM architectures previous to v7 value must be 1, to enable a simple enumeration scheme for processors that do not have a HW CPU identification register. # On 32-bit ARM 11 MPcore, ARM v7 or later systems value must be 1, that corresponds to CPUID/MPIDR registers sizes. # On ARM v8 64-bit systems value should be set to 2, that corresponds to the MPIDR_EL1 register size. If MPIDR_EL1[63:32] value is equal to 0 on all CPUs in the system, #address-cells can be set to 1, since MPIDR_EL1[63:32] bits are not used for CPUs identification. - #size-cells Usage: required Value type: Definition: must be set to 0 - cpu node Description: Describes a CPU in an ARM based system PROPERTIES - device_type Usage: required Value type: Definition: must be "cpu" - reg Usage and definition depend on ARM architecture version and configuration: # On uniprocessor ARM architectures previous to v7 this property is required and must be set to 0. # On ARM 11 MPcore based systems this property is required and matches the CPUID[11:0] register bits. Bits [11:0] in the reg cell must be set to bits [11:0] in CPU ID register. All other bits in the reg cell must be set to 0. # On 32-bit ARM v7 or later systems this property is required and matches the CPU MPIDR[23:0] register bits. Bits [23:0] in the reg cell must be set to bits [23:0] in MPIDR. All other bits in the reg cell must be set to 0. # On ARM v8 64-bit systems this property is required and matches the MPIDR_EL1 register affinity bits. * If cpus node's #address-cells property is set to 2 The first reg cell bits [7:0] must be set to bits [39:32] of MPIDR_EL1. The second reg cell bits [23:0] must be set to bits [23:0] of MPIDR_EL1. * If cpus node's #address-cells property is set to 1 The reg cell bits [23:0] must be set to bits [23:0] of MPIDR_EL1. All other bits in the reg cells must be set to 0. - compatible: Usage: required Value type: Definition: should be one of: "arm,arm710t" "arm,arm720t" "arm,arm740t" "arm,arm7ej-s" "arm,arm7tdmi" "arm,arm7tdmi-s" "arm,arm9es" "arm,arm9ej-s" "arm,arm920t" "arm,arm922t" "arm,arm925" "arm,arm926e-s" "arm,arm926ej-s" "arm,arm940t" "arm,arm946e-s" "arm,arm966e-s" "arm,arm968e-s" "arm,arm9tdmi" "arm,arm1020e" "arm,arm1020t" "arm,arm1022e" "arm,arm1026ej-s" "arm,arm1136j-s" "arm,arm1136jf-s" "arm,arm1156t2-s" "arm,arm1156t2f-s" "arm,arm1176jzf" "arm,arm1176jz-s" "arm,arm1176jzf-s" "arm,arm11mpcore" "arm,cortex-a5" "arm,cortex-a7" "arm,cortex-a8" "arm,cortex-a9" "arm,cortex-a12" "arm,cortex-a15" "arm,cortex-a17" "arm,cortex-a53" "arm,cortex-a57" "arm,cortex-m0" "arm,cortex-m0+" "arm,cortex-m1" "arm,cortex-m3" "arm,cortex-m4" "arm,cortex-r4" "arm,cortex-r5" "arm,cortex-r7" "brcm,brahma-b15" "cavium,thunder" "faraday,fa526" "intel,sa110" "intel,sa1100" "marvell,feroceon" "marvell,mohawk" "marvell,pj4a" "marvell,pj4b" "marvell,sheeva-v5" "qcom,krait" "qcom,scorpion" - enable-method Value type: Usage and definition depend on ARM architecture version. # On ARM v8 64-bit this property is required and must be one of: "psci" "spin-table" # On ARM 32-bit systems this property is optional and can be one of: "allwinner,sun6i-a31" "arm,psci" "brcm,brahma-b15" "marvell,armada-375-smp" "marvell,armada-380-smp" "marvell,armada-xp-smp" "qcom,gcc-msm8660" "qcom,kpss-acc-v1" "qcom,kpss-acc-v2" "rockchip,rk3066-smp" - cpu-release-addr Usage: required for systems that have an "enable-method" property value of "spin-table". Value type: Definition: # On ARM v8 64-bit systems must be a two cell property identifying a 64-bit zero-initialised memory location. - qcom,saw Usage: required for systems that have an "enable-method" property value of "qcom,kpss-acc-v1" or "qcom,kpss-acc-v2" Value type: Definition: Specifies the SAW[1] node associated with this CPU. - qcom,acc Usage: required for systems that have an "enable-method" property value of "qcom,kpss-acc-v1" or "qcom,kpss-acc-v2" Value type: Definition: Specifies the ACC[2] node associated with this CPU. - cpu-idle-states Usage: Optional Value type: Definition: # List of phandles to idle state nodes supported by this cpu [3]. Example 1 (dual-cluster big.LITTLE system 32-bit): cpus { #size-cells = <0>; #address-cells = <1>; cpu@0 { device_type = "cpu"; compatible = "arm,cortex-a15"; reg = <0x0>; }; cpu@1 { device_type = "cpu"; compatible = "arm,cortex-a15"; reg = <0x1>; }; cpu@100 { device_type = "cpu"; compatible = "arm,cortex-a7"; reg = <0x100>; }; cpu@101 { device_type = "cpu"; compatible = "arm,cortex-a7"; reg = <0x101>; }; }; Example 2 (Cortex-A8 uniprocessor 32-bit system): cpus { #size-cells = <0>; #address-cells = <1>; cpu@0 { device_type = "cpu"; compatible = "arm,cortex-a8"; reg = <0x0>; }; }; Example 3 (ARM 926EJ-S uniprocessor 32-bit system): cpus { #size-cells = <0>; #address-cells = <1>; cpu@0 { device_type = "cpu"; compatible = "arm,arm926ej-s"; reg = <0x0>; }; }; Example 4 (ARM Cortex-A57 64-bit system): cpus { #size-cells = <0>; #address-cells = <2>; cpu@0 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x0>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@1 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x1>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x100>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@101 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x101>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@10000 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x10000>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@10001 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x10001>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@10100 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x10100>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@10101 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x0 0x10101>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100000000 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x0>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100000001 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x1>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100000100 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x100>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100000101 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x101>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100010000 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x10000>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100010001 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x10001>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100010100 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x10100>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; cpu@100010101 { device_type = "cpu"; compatible = "arm,cortex-a57"; reg = <0x1 0x10101>; enable-method = "spin-table"; cpu-release-addr = <0 0x20000000>; }; }; -- [1] arm/msm/qcom,saw2.txt [2] arm/msm/qcom,kpss-acc.txt [3] ARM Linux kernel documentation - idle states bindings Documentation/devicetree/bindings/arm/idle-states.txt