1# SPDX-License-Identifier: (GPL-2.0) 2# Copyright 2020 Linaro Ltd. 3%YAML 1.2 4--- 5$id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml# 6$schema: http://devicetree.org/meta-schemas/core.yaml# 7 8title: Thermal cooling device binding 9 10maintainers: 11 - Amit Kucheria <amitk@kernel.org> 12 13description: | 14 Thermal management is achieved in devicetree by describing the sensor hardware 15 and the software abstraction of cooling devices and thermal zones required to 16 take appropriate action to mitigate thermal overload. 17 18 The following node types are used to completely describe a thermal management 19 system in devicetree: 20 - thermal-sensor: device that measures temperature, has SoC-specific bindings 21 - cooling-device: device used to dissipate heat either passively or actively 22 - thermal-zones: a container of the following node types used to describe all 23 thermal data for the platform 24 25 This binding describes the cooling devices. 26 27 There are essentially two ways to provide control on power dissipation: 28 - Passive cooling: by means of regulating device performance. A typical 29 passive cooling mechanism is a CPU that has dynamic voltage and frequency 30 scaling (DVFS), and uses lower frequencies as cooling states. 31 - Active cooling: by means of activating devices in order to remove the 32 dissipated heat, e.g. regulating fan speeds. 33 34 Any cooling device has a range of cooling states (i.e. different levels of 35 heat dissipation). They also have a way to determine the state of cooling in 36 which the device is. For example, a fan's cooling states correspond to the 37 different fan speeds possible. Cooling states are referred to by single 38 unsigned integers, where larger numbers mean greater heat dissipation. The 39 precise set of cooling states associated with a device should be defined in 40 a particular device's binding. 41 42select: true 43 44properties: 45 "#cooling-cells": 46 description: 47 Must be 2, in order to specify minimum and maximum cooling state used in 48 the cooling-maps reference. The first cell is the minimum cooling state 49 and the second cell is the maximum cooling state requested. 50 const: 2 51 52examples: 53 - | 54 #include <dt-bindings/interrupt-controller/arm-gic.h> 55 #include <dt-bindings/thermal/thermal.h> 56 57 // Example 1: Cpufreq cooling device on CPU0 58 cpus { 59 #address-cells = <2>; 60 #size-cells = <0>; 61 62 CPU0: cpu@0 { 63 device_type = "cpu"; 64 compatible = "qcom,kryo385"; 65 reg = <0x0 0x0>; 66 enable-method = "psci"; 67 cpu-idle-states = <&LITTLE_CPU_SLEEP_0 68 &LITTLE_CPU_SLEEP_1 69 &CLUSTER_SLEEP_0>; 70 capacity-dmips-mhz = <607>; 71 dynamic-power-coefficient = <100>; 72 qcom,freq-domain = <&cpufreq_hw 0>; 73 #cooling-cells = <2>; 74 next-level-cache = <&L2_0>; 75 L2_0: l2-cache { 76 compatible = "cache"; 77 next-level-cache = <&L3_0>; 78 L3_0: l3-cache { 79 compatible = "cache"; 80 }; 81 }; 82 }; 83 84 /* ... */ 85 86 }; 87 88 /* ... */ 89 90 thermal-zones { 91 cpu0-thermal { 92 polling-delay-passive = <250>; 93 polling-delay = <1000>; 94 95 thermal-sensors = <&tsens0 1>; 96 97 trips { 98 cpu0_alert0: trip-point0 { 99 temperature = <90000>; 100 hysteresis = <2000>; 101 type = "passive"; 102 }; 103 }; 104 105 cooling-maps { 106 map0 { 107 trip = <&cpu0_alert0>; 108 /* Corresponds to 1000MHz in OPP table */ 109 cooling-device = <&CPU0 5 5>; 110 }; 111 }; 112 }; 113 114 /* ... */ 115 }; 116... 117