# SPDX-License-Identifier: (GPL-2.0) # Copyright 2020 Linaro Ltd. %YAML 1.2 --- $id: http://devicetree.org/schemas/thermal/thermal-zones.yaml# $schema: http://devicetree.org/meta-schemas/base.yaml# title: Thermal zone maintainers: - Amit Kucheria 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 overloads. 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 thermal-zones. The polling-delay properties of a thermal-zone are bound to the maximum dT/dt (temperature derivative over time) in two situations for a thermal zone: 1. when passive cooling is activated (polling-delay-passive) 2. when the zone just needs to be monitored (polling-delay) or when active cooling is activated. The maximum dT/dt is highly bound to hardware power consumption and dissipation capability. The delays should be chosen to account for said max dT/dt, such that a device does not cross several trip boundaries unexpectedly between polls. Choosing the right polling delays shall avoid having the device in temperature ranges that may damage the silicon structures and reduce silicon lifetime. properties: $nodename: const: thermal-zones description: A /thermal-zones node is required in order to use the thermal framework to manage input from the various thermal zones in the system in order to mitigate thermal overload conditions. It does not represent a real device in the system, but acts as a container to link a thermal sensor device, platform-data regarding temperature thresholds and the mitigation actions to take when the temperature crosses those thresholds. patternProperties: # Node name is limited in size due to Linux kernel requirements - 19 # characters in total (see THERMAL_NAME_LENGTH, including terminating NUL # byte): "^[a-zA-Z][a-zA-Z0-9\\-]{1,10}-thermal$": type: object description: Each thermal zone node contains information about how frequently it must be checked, the sensor responsible for reporting temperature for this zone, one sub-node containing the various trip points for this zone and one sub-node containing all the zone cooling-maps. properties: polling-delay: $ref: /schemas/types.yaml#/definitions/uint32 description: The maximum number of milliseconds to wait between polls when checking this thermal zone. Setting this to 0 disables the polling timers setup by the thermal framework and assumes that the thermal sensors in this zone support interrupts. polling-delay-passive: $ref: /schemas/types.yaml#/definitions/uint32 description: The maximum number of milliseconds to wait between polls when checking this thermal zone while doing passive cooling. Setting this to 0 disables the polling timers setup by the thermal framework and assumes that the thermal sensors in this zone support interrupts. thermal-sensors: $ref: /schemas/types.yaml#/definitions/phandle-array maxItems: 1 description: The thermal sensor phandle and sensor specifier used to monitor this thermal zone. coefficients: $ref: /schemas/types.yaml#/definitions/uint32-array description: An array of integers containing the coefficients of a linear equation that binds all the sensors listed in this thermal zone. The linear equation used is as follows, z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn where c0, c1, .., cn are the coefficients. Coefficients default to 1 in case this property is not specified. The coefficients are ordered and are matched with sensors by means of the sensor ID. Additional coefficients are interpreted as constant offset. sustainable-power: $ref: /schemas/types.yaml#/definitions/uint32 description: An estimate of the sustainable power (in mW) that this thermal zone can dissipate at the desired control temperature. For reference, the sustainable power of a 4-inch phone is typically 2000mW, while on a 10-inch tablet is around 4500mW. trips: type: object description: This node describes a set of points in the temperature domain at which the thermal framework needs to take action. The actions to be taken are defined in another node called cooling-maps. patternProperties: "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$": type: object properties: temperature: $ref: /schemas/types.yaml#/definitions/int32 minimum: -273000 maximum: 200000 description: An integer expressing the trip temperature in millicelsius. hysteresis: $ref: /schemas/types.yaml#/definitions/uint32 description: An unsigned integer expressing the hysteresis delta with respect to the trip temperature property above, also in millicelsius. Any cooling action initiated by the framework is maintained until the temperature falls below (trip temperature - hysteresis). This potentially prevents a situation where the trip gets constantly triggered soon after cooling action is removed. type: $ref: /schemas/types.yaml#/definitions/string enum: - active # enable active cooling e.g. fans - passive # enable passive cooling e.g. throttling cpu - hot # send notification to driver - critical # send notification to driver, trigger shutdown description: | There are four valid trip types: active, passive, hot, critical. The critical trip type is used to set the maximum temperature threshold above which the HW becomes unstable and underlying firmware might even trigger a reboot. Hitting the critical threshold triggers a system shutdown. The hot trip type can be used to send a notification to the thermal driver (if a .notify callback is registered). The action to be taken is left to the driver. The passive trip type can be used to slow down HW e.g. run the CPU, GPU, bus at a lower frequency. The active trip type can be used to control other HW to help in cooling e.g. fans can be sped up or slowed down required: - temperature - hysteresis - type additionalProperties: false additionalProperties: false cooling-maps: type: object additionalProperties: false description: This node describes the action to be taken when a thermal zone crosses one of the temperature thresholds described in the trips node. The action takes the form of a mapping relation between a trip and the target cooling device state. patternProperties: "^map[-a-zA-Z0-9]*$": type: object properties: trip: $ref: /schemas/types.yaml#/definitions/phandle description: A phandle of a trip point node within this thermal zone. cooling-device: $ref: /schemas/types.yaml#/definitions/phandle-array description: A list of cooling device phandles along with the minimum and maximum cooling state specifiers for each cooling device. Using the THERMAL_NO_LIMIT (-1UL) constant in the cooling-device phandle limit specifier lets the framework use the minimum and maximum cooling state for that cooling device automatically. contribution: $ref: /schemas/types.yaml#/definitions/uint32 description: The cooling contribution to the thermal zone of the referred cooling device at the referred trip point. The contribution is a ratio of the sum of all cooling contributions within a thermal zone. required: - trip - cooling-device additionalProperties: false required: - polling-delay - polling-delay-passive - thermal-sensors - trips additionalProperties: false additionalProperties: false examples: - | #include #include // Example 1: SDM845 TSENS soc { #address-cells = <2>; #size-cells = <2>; /* ... */ tsens0: thermal-sensor@c263000 { compatible = "qcom,sdm845-tsens", "qcom,tsens-v2"; reg = <0 0x0c263000 0 0x1ff>, /* TM */ <0 0x0c222000 0 0x1ff>; /* SROT */ #qcom,sensors = <13>; interrupts = , ; interrupt-names = "uplow", "critical"; #thermal-sensor-cells = <1>; }; tsens1: thermal-sensor@c265000 { compatible = "qcom,sdm845-tsens", "qcom,tsens-v2"; reg = <0 0x0c265000 0 0x1ff>, /* TM */ <0 0x0c223000 0 0x1ff>; /* SROT */ #qcom,sensors = <8>; interrupts = , ; interrupt-names = "uplow", "critical"; #thermal-sensor-cells = <1>; }; }; /* ... */ 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"; }; cpu0_alert1: trip-point1 { temperature = <95000>; hysteresis = <2000>; type = "passive"; }; cpu0_crit: cpu_crit { temperature = <110000>; hysteresis = <1000>; type = "critical"; }; }; cooling-maps { map0 { trip = <&cpu0_alert0>; /* Corresponds to 1400MHz in OPP table */ cooling-device = <&CPU0 3 3>, <&CPU1 3 3>, <&CPU2 3 3>, <&CPU3 3 3>; }; map1 { trip = <&cpu0_alert1>; /* Corresponds to 1000MHz in OPP table */ cooling-device = <&CPU0 5 5>, <&CPU1 5 5>, <&CPU2 5 5>, <&CPU3 5 5>; }; }; }; /* ... */ cluster0-thermal { polling-delay-passive = <250>; polling-delay = <1000>; thermal-sensors = <&tsens0 5>; trips { cluster0_alert0: trip-point0 { temperature = <90000>; hysteresis = <2000>; type = "hot"; }; cluster0_crit: cluster0_crit { temperature = <110000>; hysteresis = <2000>; type = "critical"; }; }; }; /* ... */ gpu-top-thermal { polling-delay-passive = <250>; polling-delay = <1000>; thermal-sensors = <&tsens0 11>; trips { gpu1_alert0: trip-point0 { temperature = <90000>; hysteresis = <2000>; type = "hot"; }; }; }; }; ...