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1# SPDX-License-Identifier: (GPL-2.0)2# Copyright 2020 Linaro Ltd.3%YAML 1.24---5$id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml#6$schema: http://devicetree.org/meta-schemas/core.yaml#7 8title: Thermal cooling device9 10maintainers:11 - Amit Kucheria <amitk@kernel.org>12 13description: |14 Thermal management is achieved in devicetree by describing the sensor hardware15 and the software abstraction of cooling devices and thermal zones required to16 take appropriate action to mitigate thermal overload.17 18 The following node types are used to completely describe a thermal management19 system in devicetree:20 - thermal-sensor: device that measures temperature, has SoC-specific bindings21 - cooling-device: device used to dissipate heat either passively or actively22 - thermal-zones: a container of the following node types used to describe all23 thermal data for the platform24 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 typical29 passive cooling mechanism is a CPU that has dynamic voltage and frequency30 scaling (DVFS), and uses lower frequencies as cooling states.31 - Active cooling: by means of activating devices in order to remove the32 dissipated heat, e.g. regulating fan speeds.33 34 Any cooling device has a range of cooling states (i.e. different levels of35 heat dissipation). They also have a way to determine the state of cooling in36 which the device is. For example, a fan's cooling states correspond to the37 different fan speeds possible. Cooling states are referred to by single38 unsigned integers, where larger numbers mean greater heat dissipation. The39 precise set of cooling states associated with a device should be defined in40 a particular device's binding.41 42select: true43 44properties:45 "#cooling-cells":46 description:47 Must be 2, in order to specify minimum and maximum cooling state used in48 the cooling-maps reference. The first cell is the minimum cooling state49 and the second cell is the maximum cooling state requested.50 const: 251 52additionalProperties: true53 54examples:55 - |56 #include <dt-bindings/interrupt-controller/arm-gic.h>57 #include <dt-bindings/thermal/thermal.h>58 59 // Example 1: Cpufreq cooling device on CPU060 cpus {61 #address-cells = <2>;62 #size-cells = <0>;63 64 CPU0: cpu@0 {65 device_type = "cpu";66 compatible = "qcom,kryo385";67 reg = <0x0 0x0>;68 enable-method = "psci";69 cpu-idle-states = <&LITTLE_CPU_SLEEP_0>,70 <&LITTLE_CPU_SLEEP_1>,71 <&CLUSTER_SLEEP_0>;72 capacity-dmips-mhz = <607>;73 dynamic-power-coefficient = <100>;74 qcom,freq-domain = <&cpufreq_hw 0>;75 #cooling-cells = <2>;76 next-level-cache = <&L2_0>;77 L2_0: l2-cache {78 compatible = "cache";79 cache-unified;80 cache-level = <2>;81 next-level-cache = <&L3_0>;82 L3_0: l3-cache {83 compatible = "cache";84 cache-unified;85 cache-level = <3>;86 };87 };88 };89 90 /* ... */91 92 };93 94 /* ... */95 96 thermal-zones {97 cpu0-thermal {98 polling-delay-passive = <250>;99 polling-delay = <1000>;100 101 thermal-sensors = <&tsens0 1>;102 103 trips {104 cpu0_alert0: trip-point0 {105 temperature = <90000>;106 hysteresis = <2000>;107 type = "passive";108 };109 };110 111 cooling-maps {112 map0 {113 trip = <&cpu0_alert0>;114 /* Corresponds to 1000MHz in OPP table */115 cooling-device = <&CPU0 5 5>;116 };117 };118 };119 120 /* ... */121 };122...123