1 # SPDX-License-Identifier: (GPL-2.0)
2 # Copyright 2020 Linaro Ltd.
5 $id: http://devicetree.org/schemas/thermal/thermal-zones.yaml#
6 $schema: http://devicetree.org/meta-schemas/base.yaml#
11 - Daniel Lezcano <daniel.lezcano@linaro.org>
14 Thermal management is achieved in devicetree by describing the sensor hardware
15 and the software abstraction of cooling devices and thermal zones required to
16 take appropriate action to mitigate thermal overloads.
18 The following node types are used to completely describe a thermal management
20 - thermal-sensor: device that measures temperature, has SoC-specific bindings
21 - cooling-device: device used to dissipate heat either passively or actively
22 - thermal-zones: a container of the following node types used to describe all
23 thermal data for the platform
25 This binding describes the thermal-zones.
27 The polling-delay properties of a thermal-zone are bound to the maximum dT/dt
28 (temperature derivative over time) in two situations for a thermal zone:
29 1. when passive cooling is activated (polling-delay-passive)
30 2. when the zone just needs to be monitored (polling-delay) or when
31 active cooling is activated.
33 The maximum dT/dt is highly bound to hardware power consumption and
34 dissipation capability. The delays should be chosen to account for said
35 max dT/dt, such that a device does not cross several trip boundaries
36 unexpectedly between polls. Choosing the right polling delays shall avoid
37 having the device in temperature ranges that may damage the silicon structures
38 and reduce silicon lifetime.
44 A /thermal-zones node is required in order to use the thermal framework to
45 manage input from the various thermal zones in the system in order to
46 mitigate thermal overload conditions. It does not represent a real device
47 in the system, but acts as a container to link a thermal sensor device,
48 platform-data regarding temperature thresholds and the mitigation actions
49 to take when the temperature crosses those thresholds.
52 # Node name is limited in size due to Linux kernel requirements - 19
53 # characters in total (see THERMAL_NAME_LENGTH, including terminating NUL
55 "^[a-zA-Z][a-zA-Z0-9\\-]{1,10}-thermal$":
58 Each thermal zone node contains information about how frequently it
59 must be checked, the sensor responsible for reporting temperature for
60 this zone, one sub-node containing the various trip points for this
61 zone and one sub-node containing all the zone cooling-maps.
65 $ref: /schemas/types.yaml#/definitions/uint32
67 The maximum number of milliseconds to wait between polls when
68 checking this thermal zone. Setting this to 0 disables the polling
69 timers setup by the thermal framework and assumes that the thermal
70 sensors in this zone support interrupts.
72 polling-delay-passive:
73 $ref: /schemas/types.yaml#/definitions/uint32
75 The maximum number of milliseconds to wait between polls when
76 checking this thermal zone while doing passive cooling. Setting
77 this to 0 disables the polling timers setup by the thermal
78 framework and assumes that the thermal sensors in this zone
82 $ref: /schemas/types.yaml#/definitions/string
84 The action the OS should perform after the critical temperature is reached.
85 By default the system will shutdown as a safe action to prevent damage
86 to the hardware, if the property is not set.
87 The shutdown action should be always the default and preferred one.
88 Choose 'reboot' with care, as the hardware may be in thermal stress,
89 thus leading to infinite reboots that may cause damage to the hardware.
90 Make sure the firmware/bootloader will act as the last resort and take
91 over the thermal control.
98 $ref: /schemas/types.yaml#/definitions/phandle-array
101 The thermal sensor phandle and sensor specifier used to monitor this
105 $ref: /schemas/types.yaml#/definitions/uint32-array
107 An array of integers containing the coefficients of a linear equation
108 that binds all the sensors listed in this thermal zone.
110 The linear equation used is as follows,
111 z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn
112 where c0, c1, .., cn are the coefficients.
114 Coefficients default to 1 in case this property is not specified. The
115 coefficients are ordered and are matched with sensors by means of the
116 sensor ID. Additional coefficients are interpreted as constant offset.
119 $ref: /schemas/types.yaml#/definitions/uint32
121 An estimate of the sustainable power (in mW) that this thermal zone
122 can dissipate at the desired control temperature. For reference, the
123 sustainable power of a 4-inch phone is typically 2000mW, while on a
124 10-inch tablet is around 4500mW.
129 This node describes a set of points in the temperature domain at
130 which the thermal framework needs to take action. The actions to
131 be taken are defined in another node called cooling-maps.
134 "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$":
139 $ref: /schemas/types.yaml#/definitions/int32
143 An integer expressing the trip temperature in millicelsius.
146 $ref: /schemas/types.yaml#/definitions/uint32
148 An unsigned integer expressing the hysteresis delta with
149 respect to the trip temperature property above, also in
150 millicelsius. Any cooling action initiated by the framework is
151 maintained until the temperature falls below
152 (trip temperature - hysteresis). This potentially prevents a
153 situation where the trip gets constantly triggered soon after
154 cooling action is removed.
157 $ref: /schemas/types.yaml#/definitions/string
159 - active # enable active cooling e.g. fans
160 - passive # enable passive cooling e.g. throttling cpu
161 - hot # send notification to driver
162 - critical # send notification to driver, trigger shutdown
164 There are four valid trip types: active, passive, hot,
167 The critical trip type is used to set the maximum
168 temperature threshold above which the HW becomes
169 unstable and underlying firmware might even trigger a
170 reboot. Hitting the critical threshold triggers a system
173 The hot trip type can be used to send a notification to
174 the thermal driver (if a .notify callback is registered).
175 The action to be taken is left to the driver.
177 The passive trip type can be used to slow down HW e.g. run
178 the CPU, GPU, bus at a lower frequency.
180 The active trip type can be used to control other HW to
181 help in cooling e.g. fans can be sped up or slowed down
187 additionalProperties: false
189 additionalProperties: false
193 additionalProperties: false
195 This node describes the action to be taken when a thermal zone
196 crosses one of the temperature thresholds described in the trips
197 node. The action takes the form of a mapping relation between a
198 trip and the target cooling device state.
201 "^map[-a-zA-Z0-9]*$":
206 $ref: /schemas/types.yaml#/definitions/phandle
208 A phandle of a trip point node within this thermal zone.
211 $ref: /schemas/types.yaml#/definitions/phandle-array
213 A list of cooling device phandles along with the minimum
214 and maximum cooling state specifiers for each cooling
215 device. Using the THERMAL_NO_LIMIT (-1UL) constant in the
216 cooling-device phandle limit specifier lets the framework
217 use the minimum and maximum cooling state for that cooling
218 device automatically.
221 $ref: /schemas/types.yaml#/definitions/uint32
223 The cooling contribution to the thermal zone of the referred
224 cooling device at the referred trip point. The contribution is
225 a ratio of the sum of all cooling contributions within a
231 additionalProperties: false
236 additionalProperties: false
238 additionalProperties: false
242 #include <dt-bindings/interrupt-controller/arm-gic.h>
243 #include <dt-bindings/thermal/thermal.h>
245 // Example 1: SDM845 TSENS
247 #address-cells = <2>;
252 tsens0: thermal-sensor@c263000 {
253 compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
254 reg = <0 0x0c263000 0 0x1ff>, /* TM */
255 <0 0x0c222000 0 0x1ff>; /* SROT */
256 #qcom,sensors = <13>;
257 interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>,
258 <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>;
259 interrupt-names = "uplow", "critical";
260 #thermal-sensor-cells = <1>;
263 tsens1: thermal-sensor@c265000 {
264 compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
265 reg = <0 0x0c265000 0 0x1ff>, /* TM */
266 <0 0x0c223000 0 0x1ff>; /* SROT */
268 interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>,
269 <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>;
270 interrupt-names = "uplow", "critical";
271 #thermal-sensor-cells = <1>;
279 polling-delay-passive = <250>;
280 polling-delay = <1000>;
282 thermal-sensors = <&tsens0 1>;
285 cpu0_alert0: trip-point0 {
286 temperature = <90000>;
291 cpu0_alert1: trip-point1 {
292 temperature = <95000>;
297 cpu0_crit: cpu_crit {
298 temperature = <110000>;
306 trip = <&cpu0_alert0>;
307 /* Corresponds to 1400MHz in OPP table */
308 cooling-device = <&CPU0 3 3>, <&CPU1 3 3>,
309 <&CPU2 3 3>, <&CPU3 3 3>;
313 trip = <&cpu0_alert1>;
314 /* Corresponds to 1000MHz in OPP table */
315 cooling-device = <&CPU0 5 5>, <&CPU1 5 5>,
316 <&CPU2 5 5>, <&CPU3 5 5>;
324 polling-delay-passive = <250>;
325 polling-delay = <1000>;
327 thermal-sensors = <&tsens0 5>;
330 cluster0_alert0: trip-point0 {
331 temperature = <90000>;
335 cluster0_crit: cluster0_crit {
336 temperature = <110000>;
346 polling-delay-passive = <250>;
347 polling-delay = <1000>;
349 thermal-sensors = <&tsens0 11>;
352 gpu1_alert0: trip-point0 {
353 temperature = <90000>;