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- cpus.txt
=================
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"
"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-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].
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