| # 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: |
| - Daniel Lezcano <daniel.lezcano@linaro.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 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. |
| |
| critical-action: |
| $ref: /schemas/types.yaml#/definitions/string |
| description: | |
| The action the OS should perform after the critical temperature is reached. |
| By default the system will shutdown as a safe action to prevent damage |
| to the hardware, if the property is not set. |
| The shutdown action should be always the default and preferred one. |
| Choose 'reboot' with care, as the hardware may be in thermal stress, |
| thus leading to infinite reboots that may cause damage to the hardware. |
| Make sure the firmware/bootloader will act as the last resort and take |
| over the thermal control. |
| |
| enum: |
| - shutdown |
| - reboot |
| |
| 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: |
| - thermal-sensors |
| |
| additionalProperties: false |
| |
| additionalProperties: false |
| |
| examples: |
| - | |
| #include <dt-bindings/interrupt-controller/arm-gic.h> |
| #include <dt-bindings/thermal/thermal.h> |
| |
| // 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 = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>, |
| <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>; |
| 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 = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>, |
| <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>; |
| 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"; |
| }; |
| }; |
| }; |
| }; |
| ... |
