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