5 The device tree allows to describe the layout of CPUs in a system through
6 the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
7 defining properties for every cpu.
9 Bindings for CPU nodes follow the ePAPR v1.1 standard, available from:
11 https://www.power.org/documentation/epapr-version-1-1/
13 with updates for 32-bit and 64-bit ARM systems provided in this document.
15 ================================
16 Convention used in this document
17 ================================
19 This document follows the conventions described in the ePAPR v1.1, with
22 - square brackets define bitfields, eg reg[7:0] value of the bitfield in
23 the reg property contained in bits 7 down to 0
25 =====================================
26 cpus and cpu node bindings definition
27 =====================================
29 The ARM architecture, in accordance with the ePAPR, requires the cpus and cpu
30 nodes to be present and contain the properties described below.
34 Description: Container of cpu nodes
36 The node name must be "cpus".
38 A cpus node must define the following properties:
44 Definition depends on ARM architecture version and
47 # On uniprocessor ARM architectures previous to v7
48 value must be 1, to enable a simple enumeration
49 scheme for processors that do not have a HW CPU
50 identification register.
51 # On 32-bit ARM 11 MPcore, ARM v7 or later systems
52 value must be 1, that corresponds to CPUID/MPIDR
54 # On ARM v8 64-bit systems value should be set to 2,
55 that corresponds to the MPIDR_EL1 register size.
56 If MPIDR_EL1[63:32] value is equal to 0 on all CPUs
57 in the system, #address-cells can be set to 1, since
58 MPIDR_EL1[63:32] bits are not used for CPUs
63 Definition: must be set to 0
67 Description: Describes a CPU in an ARM based system
74 Definition: must be "cpu"
76 Usage and definition depend on ARM architecture version and
79 # On uniprocessor ARM architectures previous to v7
80 this property is required and must be set to 0.
82 # On ARM 11 MPcore based systems this property is
83 required and matches the CPUID[11:0] register bits.
85 Bits [11:0] in the reg cell must be set to
86 bits [11:0] in CPU ID register.
88 All other bits in the reg cell must be set to 0.
90 # On 32-bit ARM v7 or later systems this property is
91 required and matches the CPU MPIDR[23:0] register
94 Bits [23:0] in the reg cell must be set to
97 All other bits in the reg cell must be set to 0.
99 # On ARM v8 64-bit systems this property is required
100 and matches the MPIDR_EL1 register affinity bits.
102 * If cpus node's #address-cells property is set to 2
104 The first reg cell bits [7:0] must be set to
105 bits [39:32] of MPIDR_EL1.
107 The second reg cell bits [23:0] must be set to
108 bits [23:0] of MPIDR_EL1.
110 * If cpus node's #address-cells property is set to 1
112 The reg cell bits [23:0] must be set to bits [23:0]
115 All other bits in the reg cells must be set to 0.
120 Definition: should be one of:
182 "nvidia,tegra132-denver"
183 "nvidia,tegra186-denver"
188 Value type: <stringlist>
189 Usage and definition depend on ARM architecture version.
190 # On ARM v8 64-bit this property is required and must
194 # On ARM 32-bit systems this property is optional and
196 "allwinner,sun6i-a31"
197 "allwinner,sun8i-a23"
199 "brcm,bcm11351-cpu-method"
203 "marvell,armada-375-smp"
204 "marvell,armada-380-smp"
205 "marvell,armada-390-smp"
206 "marvell,armada-xp-smp"
207 "marvell,98dx3236-smp"
208 "mediatek,mt6589-smp"
209 "mediatek,mt81xx-tz-smp"
214 "rockchip,rk3036-smp"
215 "rockchip,rk3066-smp"
219 Usage: required for systems that have an "enable-method"
220 property value of "spin-table".
221 Value type: <prop-encoded-array>
223 # On ARM v8 64-bit systems must be a two cell
224 property identifying a 64-bit zero-initialised
228 Usage: required for systems that have an "enable-method"
229 property value of "qcom,kpss-acc-v1" or
231 Value type: <phandle>
232 Definition: Specifies the SAW[1] node associated with this CPU.
235 Usage: required for systems that have an "enable-method"
236 property value of "qcom,kpss-acc-v1" or
238 Value type: <phandle>
239 Definition: Specifies the ACC[2] node associated with this CPU.
243 Value type: <prop-encoded-array>
245 # List of phandles to idle state nodes supported
252 # u32 value representing CPU capacity [3] in
253 DMIPS/MHz, relative to highest capacity-dmips-mhz
257 Usage: optional for systems that have an "enable-method"
258 property value of "rockchip,rk3066-smp"
259 While optional, it is the preferred way to get access to
260 the cpu-core power-domains.
261 Value type: <phandle>
262 Definition: Specifies the syscon node controlling the cpu core
265 - dynamic-power-coefficient
267 Value type: <prop-encoded-array>
268 Definition: A u32 value that represents the running time dynamic
269 power coefficient in units of mW/MHz/uV^2. The
270 coefficient can either be calculated from power
271 measurements or derived by analysis.
273 The dynamic power consumption of the CPU is
274 proportional to the square of the Voltage (V) and
275 the clock frequency (f). The coefficient is used to
276 calculate the dynamic power as below -
278 Pdyn = dynamic-power-coefficient * V^2 * f
280 where voltage is in uV, frequency is in MHz.
282 Example 1 (dual-cluster big.LITTLE system 32-bit):
286 #address-cells = <1>;
290 compatible = "arm,cortex-a15";
296 compatible = "arm,cortex-a15";
302 compatible = "arm,cortex-a7";
308 compatible = "arm,cortex-a7";
313 Example 2 (Cortex-A8 uniprocessor 32-bit system):
317 #address-cells = <1>;
321 compatible = "arm,cortex-a8";
326 Example 3 (ARM 926EJ-S uniprocessor 32-bit system):
330 #address-cells = <1>;
334 compatible = "arm,arm926ej-s";
339 Example 4 (ARM Cortex-A57 64-bit system):
343 #address-cells = <2>;
347 compatible = "arm,cortex-a57";
349 enable-method = "spin-table";
350 cpu-release-addr = <0 0x20000000>;
355 compatible = "arm,cortex-a57";
357 enable-method = "spin-table";
358 cpu-release-addr = <0 0x20000000>;
363 compatible = "arm,cortex-a57";
365 enable-method = "spin-table";
366 cpu-release-addr = <0 0x20000000>;
371 compatible = "arm,cortex-a57";
373 enable-method = "spin-table";
374 cpu-release-addr = <0 0x20000000>;
379 compatible = "arm,cortex-a57";
381 enable-method = "spin-table";
382 cpu-release-addr = <0 0x20000000>;
387 compatible = "arm,cortex-a57";
389 enable-method = "spin-table";
390 cpu-release-addr = <0 0x20000000>;
395 compatible = "arm,cortex-a57";
397 enable-method = "spin-table";
398 cpu-release-addr = <0 0x20000000>;
403 compatible = "arm,cortex-a57";
405 enable-method = "spin-table";
406 cpu-release-addr = <0 0x20000000>;
411 compatible = "arm,cortex-a57";
413 enable-method = "spin-table";
414 cpu-release-addr = <0 0x20000000>;
419 compatible = "arm,cortex-a57";
421 enable-method = "spin-table";
422 cpu-release-addr = <0 0x20000000>;
427 compatible = "arm,cortex-a57";
429 enable-method = "spin-table";
430 cpu-release-addr = <0 0x20000000>;
435 compatible = "arm,cortex-a57";
437 enable-method = "spin-table";
438 cpu-release-addr = <0 0x20000000>;
443 compatible = "arm,cortex-a57";
445 enable-method = "spin-table";
446 cpu-release-addr = <0 0x20000000>;
451 compatible = "arm,cortex-a57";
453 enable-method = "spin-table";
454 cpu-release-addr = <0 0x20000000>;
459 compatible = "arm,cortex-a57";
461 enable-method = "spin-table";
462 cpu-release-addr = <0 0x20000000>;
467 compatible = "arm,cortex-a57";
469 enable-method = "spin-table";
470 cpu-release-addr = <0 0x20000000>;
475 [1] arm/msm/qcom,saw2.txt
476 [2] arm/msm/qcom,kpss-acc.txt
477 [3] ARM Linux kernel documentation - idle states bindings
478 Documentation/devicetree/bindings/arm/idle-states.txt
479 [3] ARM Linux kernel documentation - cpu capacity bindings
480 Documentation/devicetree/bindings/arm/cpu-capacity.txt