| # SPDX-License-Identifier: (GPL-2.0) |
| # Copyright 2020 Linaro Ltd. |
| %YAML 1.2 |
| --- |
| $id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml# |
| $schema: http://devicetree.org/meta-schemas/core.yaml# |
| |
| title: Thermal cooling device binding |
| |
| maintainers: |
| - Amit Kucheria <amitk@kernel.org> |
| |
| description: | |
| Thermal management is achieved in devicetree by describing the sensor hardware |
| and the software abstraction of cooling devices and thermal zones required to |
| take appropriate action to mitigate thermal overload. |
| |
| The following node types are used to completely describe a thermal management |
| system in devicetree: |
| - thermal-sensor: device that measures temperature, has SoC-specific bindings |
| - cooling-device: device used to dissipate heat either passively or actively |
| - thermal-zones: a container of the following node types used to describe all |
| thermal data for the platform |
| |
| This binding describes the cooling devices. |
| |
| There are essentially two ways to provide control on power dissipation: |
| - Passive cooling: by means of regulating device performance. A typical |
| passive cooling mechanism is a CPU that has dynamic voltage and frequency |
| scaling (DVFS), and uses lower frequencies as cooling states. |
| - Active cooling: by means of activating devices in order to remove the |
| dissipated heat, e.g. regulating fan speeds. |
| |
| Any cooling device has a range of cooling states (i.e. different levels of |
| heat dissipation). They also have a way to determine the state of cooling in |
| which the device is. For example, a fan's cooling states correspond to the |
| different fan speeds possible. Cooling states are referred to by single |
| unsigned integers, where larger numbers mean greater heat dissipation. The |
| precise set of cooling states associated with a device should be defined in |
| a particular device's binding. |
| |
| select: true |
| |
| properties: |
| "#cooling-cells": |
| description: |
| Must be 2, in order to specify minimum and maximum cooling state used in |
| the cooling-maps reference. The first cell is the minimum cooling state |
| and the second cell is the maximum cooling state requested. |
| const: 2 |
| |
| additionalProperties: true |
| |
| examples: |
| - | |
| #include <dt-bindings/interrupt-controller/arm-gic.h> |
| #include <dt-bindings/thermal/thermal.h> |
| |
| // Example 1: Cpufreq cooling device on CPU0 |
| cpus { |
| #address-cells = <2>; |
| #size-cells = <0>; |
| |
| CPU0: cpu@0 { |
| device_type = "cpu"; |
| compatible = "qcom,kryo385"; |
| reg = <0x0 0x0>; |
| enable-method = "psci"; |
| cpu-idle-states = <&LITTLE_CPU_SLEEP_0>, |
| <&LITTLE_CPU_SLEEP_1>, |
| <&CLUSTER_SLEEP_0>; |
| capacity-dmips-mhz = <607>; |
| dynamic-power-coefficient = <100>; |
| qcom,freq-domain = <&cpufreq_hw 0>; |
| #cooling-cells = <2>; |
| next-level-cache = <&L2_0>; |
| L2_0: l2-cache { |
| compatible = "cache"; |
| next-level-cache = <&L3_0>; |
| L3_0: l3-cache { |
| compatible = "cache"; |
| }; |
| }; |
| }; |
| |
| /* ... */ |
| |
| }; |
| |
| /* ... */ |
| |
| thermal-zones { |
| cpu0-thermal { |
| polling-delay-passive = <250>; |
| polling-delay = <1000>; |
| |
| thermal-sensors = <&tsens0 1>; |
| |
| trips { |
| cpu0_alert0: trip-point0 { |
| temperature = <90000>; |
| hysteresis = <2000>; |
| type = "passive"; |
| }; |
| }; |
| |
| cooling-maps { |
| map0 { |
| trip = <&cpu0_alert0>; |
| /* Corresponds to 1000MHz in OPP table */ |
| cooling-device = <&CPU0 5 5>; |
| }; |
| }; |
| }; |
| |
| /* ... */ |
| }; |
| ... |