--- /dev/null
+=================
+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: <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-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"
+ "nvidia,tegra132-denver"
+ "qcom,krait"
+ "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:
+ "allwinner,sun6i-a31"
+ "arm,psci"
+ "brcm,brahma-b15"
+ "marvell,armada-375-smp"
+ "marvell,armada-380-smp"
+ "marvell,armada-390-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: <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].
+
+ - 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.
+
+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
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