119 lines
4.2 KiB
YAML
119 lines
4.2 KiB
YAML
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# 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 <amitk@kernel.org>
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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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