dt-bindings: thermal: Add yaml bindings for thermal zones
As part of moving the thermal bindings to YAML, split it up into 3 bindings: thermal sensors, cooling devices and thermal zones. The thermal-zone binding is a software abstraction to capture the properties of each zone - how often they should be checked, the temperature thresholds (trips) at which mitigation actions need to be taken and the level of mitigation needed at those thresholds. Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Link: https://lore.kernel.org/r/44e5c68bc654ccaf88945f70dc875fa186dd1480.1585748882.git.amit.kucheria@linaro.org
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Amit Kucheria
Daniel Lezcano
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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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$id: http://devicetree.org/schemas/thermal/thermal-zones.yaml#
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$schema: http://devicetree.org/meta-schemas/base.yaml#
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title: Thermal zone 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 overloads.
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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 thermal-zones.
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The polling-delay properties of a thermal-zone are bound to the maximum dT/dt
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(temperature derivative over time) in two situations for a thermal zone:
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1. when passive cooling is activated (polling-delay-passive)
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2. when the zone just needs to be monitored (polling-delay) or when
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active cooling is activated.
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The maximum dT/dt is highly bound to hardware power consumption and
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dissipation capability. The delays should be chosen to account for said
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max dT/dt, such that a device does not cross several trip boundaries
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unexpectedly between polls. Choosing the right polling delays shall avoid
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having the device in temperature ranges that may damage the silicon structures
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and reduce silicon lifetime.
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properties:
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$nodename:
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const: thermal-zones
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description:
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A /thermal-zones node is required in order to use the thermal framework to
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manage input from the various thermal zones in the system in order to
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mitigate thermal overload conditions. It does not represent a real device
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in the system, but acts as a container to link a thermal sensor device,
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platform-data regarding temperature thresholds and the mitigation actions
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to take when the temperature crosses those thresholds.
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patternProperties:
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"^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
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type: object
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description:
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Each thermal zone node contains information about how frequently it
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must be checked, the sensor responsible for reporting temperature for
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this zone, one sub-node containing the various trip points for this
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zone and one sub-node containing all the zone cooling-maps.
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properties:
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polling-delay:
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$ref: /schemas/types.yaml#/definitions/uint32
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description:
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The maximum number of milliseconds to wait between polls when
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checking this thermal zone. Setting this to 0 disables the polling
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timers setup by the thermal framework and assumes that the thermal
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sensors in this zone support interrupts.
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polling-delay-passive:
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$ref: /schemas/types.yaml#/definitions/uint32
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description:
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The maximum number of milliseconds to wait between polls when
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checking this thermal zone while doing passive cooling. Setting
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this to 0 disables the polling timers setup by the thermal
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framework and assumes that the thermal sensors in this zone
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support interrupts.
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thermal-sensors:
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$ref: /schemas/types.yaml#/definitions/phandle-array
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maxItems: 1
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description:
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The thermal sensor phandle and sensor specifier used to monitor this
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thermal zone.
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coefficients:
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$ref: /schemas/types.yaml#/definitions/uint32-array
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description:
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An array of integers containing the coefficients of a linear equation
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that binds all the sensors listed in this thermal zone.
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The linear equation used is as follows,
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z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn
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where c0, c1, .., cn are the coefficients.
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Coefficients default to 1 in case this property is not specified. The
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coefficients are ordered and are matched with sensors by means of the
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sensor ID. Additional coefficients are interpreted as constant offset.
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sustainable-power:
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$ref: /schemas/types.yaml#/definitions/uint32
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description:
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An estimate of the sustainable power (in mW) that this thermal zone
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can dissipate at the desired control temperature. For reference, the
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sustainable power of a 4-inch phone is typically 2000mW, while on a
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10-inch tablet is around 4500mW.
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trips:
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type: object
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description:
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This node describes a set of points in the temperature domain at
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which the thermal framework needs to take action. The actions to
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be taken are defined in another node called cooling-maps.
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patternProperties:
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"^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$":
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type: object
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properties:
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temperature:
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$ref: /schemas/types.yaml#/definitions/int32
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minimum: -273000
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maximum: 200000
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description:
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An integer expressing the trip temperature in millicelsius.
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hysteresis:
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$ref: /schemas/types.yaml#/definitions/uint32
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description:
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An unsigned integer expressing the hysteresis delta with
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respect to the trip temperature property above, also in
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millicelsius. Any cooling action initiated by the framework is
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maintained until the temperature falls below
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(trip temperature - hysteresis). This potentially prevents a
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situation where the trip gets constantly triggered soon after
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cooling action is removed.
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type:
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$ref: /schemas/types.yaml#/definitions/string
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enum:
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- active # enable active cooling e.g. fans
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- passive # enable passive cooling e.g. throttling cpu
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- hot # send notification to driver
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- critical # send notification to driver, trigger shutdown
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description: |
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There are four valid trip types: active, passive, hot,
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critical.
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The critical trip type is used to set the maximum
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temperature threshold above which the HW becomes
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unstable and underlying firmware might even trigger a
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reboot. Hitting the critical threshold triggers a system
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shutdown.
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The hot trip type can be used to send a notification to
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the thermal driver (if a .notify callback is registered).
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The action to be taken is left to the driver.
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The passive trip type can be used to slow down HW e.g. run
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the CPU, GPU, bus at a lower frequency.
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The active trip type can be used to control other HW to
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help in cooling e.g. fans can be sped up or slowed down
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required:
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- temperature
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- hysteresis
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- type
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additionalProperties: false
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additionalProperties: false
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cooling-maps:
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type: object
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description:
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This node describes the action to be taken when a thermal zone
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crosses one of the temperature thresholds described in the trips
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node. The action takes the form of a mapping relation between a
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trip and the target cooling device state.
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patternProperties:
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"^map[-a-zA-Z0-9]*$":
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type: object
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properties:
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trip:
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$ref: /schemas/types.yaml#/definitions/phandle
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description:
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A phandle of a trip point node within this thermal zone.
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cooling-device:
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$ref: /schemas/types.yaml#/definitions/phandle-array
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description:
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A list of cooling device phandles along with the minimum
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and maximum cooling state specifiers for each cooling
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device. Using the THERMAL_NO_LIMIT (-1UL) constant in the
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cooling-device phandle limit specifier lets the framework
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use the minimum and maximum cooling state for that cooling
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device automatically.
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contribution:
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$ref: /schemas/types.yaml#/definitions/uint32
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minimum: 0
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maximum: 100
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description:
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The percentage contribution of the cooling devices at the
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specific trip temperature referenced in this map
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to this thermal zone
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required:
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- trip
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- cooling-device
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additionalProperties: false
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required:
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- polling-delay
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- polling-delay-passive
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- thermal-sensors
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- trips
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additionalProperties: false
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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: SDM845 TSENS
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soc: soc@0 {
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#address-cells = <2>;
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#size-cells = <2>;
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/* ... */
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tsens0: thermal-sensor@c263000 {
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compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
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reg = <0 0x0c263000 0 0x1ff>, /* TM */
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<0 0x0c222000 0 0x1ff>; /* SROT */
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#qcom,sensors = <13>;
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interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>,
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<GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>;
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interrupt-names = "uplow", "critical";
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#thermal-sensor-cells = <1>;
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};
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tsens1: thermal-sensor@c265000 {
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compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
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reg = <0 0x0c265000 0 0x1ff>, /* TM */
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<0 0x0c223000 0 0x1ff>; /* SROT */
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#qcom,sensors = <8>;
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interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>,
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<GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>;
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interrupt-names = "uplow", "critical";
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#thermal-sensor-cells = <1>;
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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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cpu0_alert1: trip-point1 {
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temperature = <95000>;
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hysteresis = <2000>;
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type = "passive";
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};
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cpu0_crit: cpu_crit {
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temperature = <110000>;
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hysteresis = <1000>;
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type = "critical";
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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 1400MHz in OPP table */
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cooling-device = <&CPU0 3 3>, <&CPU1 3 3>,
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<&CPU2 3 3>, <&CPU3 3 3>;
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};
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map1 {
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trip = <&cpu0_alert1>;
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/* Corresponds to 1000MHz in OPP table */
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cooling-device = <&CPU0 5 5>, <&CPU1 5 5>,
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<&CPU2 5 5>, <&CPU3 5 5>;
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};
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};
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};
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/* ... */
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cluster0-thermal {
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polling-delay-passive = <250>;
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polling-delay = <1000>;
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thermal-sensors = <&tsens0 5>;
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trips {
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cluster0_alert0: trip-point0 {
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temperature = <90000>;
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hysteresis = <2000>;
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type = "hot";
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};
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cluster0_crit: cluster0_crit {
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temperature = <110000>;
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hysteresis = <2000>;
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type = "critical";
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};
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};
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};
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/* ... */
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gpu-top-thermal {
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polling-delay-passive = <250>;
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polling-delay = <1000>;
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thermal-sensors = <&tsens0 11>;
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trips {
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gpu1_alert0: trip-point0 {
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temperature = <90000>;
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hysteresis = <2000>;
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type = "hot";
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};
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};
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};
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};
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...
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