| ================= |
| 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 Devicetree Specification, available from: |
| |
| https://www.devicetree.org/specifications/ |
| |
| 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 Devicetree |
| Specification, 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 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 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: <u32> |
| Definition: must be set to 0 |
| |
| - cpu node |
| |
| Description: Describes a CPU in an ARM based system |
| |
| PROPERTIES |
| |
| - device_type |
| Usage: required |
| Value type: <string> |
| 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: <string> |
| 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-a72" |
| "arm,cortex-a73" |
| "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" |
| "brcm,brahma-b53" |
| "brcm,vulcan" |
| "cavium,thunder" |
| "cavium,thunder2" |
| "faraday,fa526" |
| "intel,sa110" |
| "intel,sa1100" |
| "marvell,feroceon" |
| "marvell,mohawk" |
| "marvell,pj4a" |
| "marvell,pj4b" |
| "marvell,sheeva-v5" |
| "nvidia,tegra132-denver" |
| "nvidia,tegra186-denver" |
| "qcom,krait" |
| "qcom,kryo" |
| "qcom,kryo385" |
| "qcom,scorpion" |
| - enable-method |
| Value type: <stringlist> |
| 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: |
| "actions,s500-smp" |
| "allwinner,sun6i-a31" |
| "allwinner,sun8i-a23" |
| "allwinner,sun9i-a80-smp" |
| "amlogic,meson8-smp" |
| "amlogic,meson8b-smp" |
| "arm,realview-smp" |
| "brcm,bcm11351-cpu-method" |
| "brcm,bcm23550" |
| "brcm,bcm2836-smp" |
| "brcm,bcm-nsp-smp" |
| "brcm,brahma-b15" |
| "marvell,armada-375-smp" |
| "marvell,armada-380-smp" |
| "marvell,armada-390-smp" |
| "marvell,armada-xp-smp" |
| "marvell,98dx3236-smp" |
| "mediatek,mt6589-smp" |
| "mediatek,mt81xx-tz-smp" |
| "qcom,gcc-msm8660" |
| "qcom,kpss-acc-v1" |
| "qcom,kpss-acc-v2" |
| "renesas,apmu" |
| "rockchip,rk3036-smp" |
| "rockchip,rk3066-smp" |
| "ste,dbx500-smp" |
| |
| - cpu-release-addr |
| Usage: required for systems that have an "enable-method" |
| property value of "spin-table". |
| Value type: <prop-encoded-array> |
| 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: <phandle> |
| 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: <phandle> |
| Definition: Specifies the ACC[2] node associated with this CPU. |
| |
| - cpu-idle-states |
| Usage: Optional |
| Value type: <prop-encoded-array> |
| Definition: |
| # List of phandles to idle state nodes supported |
| by this cpu [3]. |
| |
| - capacity-dmips-mhz |
| Usage: Optional |
| Value type: <u32> |
| Definition: |
| # u32 value representing CPU capacity [4] in |
| DMIPS/MHz, relative to highest capacity-dmips-mhz |
| in the system. |
| |
| - rockchip,pmu |
| Usage: optional for systems that have an "enable-method" |
| property value of "rockchip,rk3066-smp" |
| While optional, it is the preferred way to get access to |
| the cpu-core power-domains. |
| Value type: <phandle> |
| Definition: Specifies the syscon node controlling the cpu core |
| power domains. |
| |
| - dynamic-power-coefficient |
| Usage: optional |
| Value type: <prop-encoded-array> |
| Definition: A u32 value that represents the running time dynamic |
| power coefficient in units of mW/MHz/uV^2. The |
| coefficient can either be calculated from power |
| measurements or derived by analysis. |
| |
| The dynamic power consumption of the CPU is |
| proportional to the square of the Voltage (V) and |
| the clock frequency (f). The coefficient is used to |
| calculate the dynamic power as below - |
| |
| Pdyn = dynamic-power-coefficient * V^2 * f |
| |
| where voltage is in uV, frequency is in MHz. |
| |
| 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 |
| [4] ARM Linux kernel documentation - cpu capacity bindings |
| Documentation/devicetree/bindings/arm/cpu-capacity.txt |
