1# SPDX-License-Identifier: (GPL-2.0) 2# Copyright 2020 Linaro Ltd. 3%YAML 1.2 4--- 5$id: http://devicetree.org/schemas/thermal/thermal-zones.yaml# 6$schema: http://devicetree.org/meta-schemas/base.yaml# 7 8title: Thermal zone binding 9 10maintainers: 11 - Amit Kucheria <amitk@kernel.org> 12 13description: | 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. 17 18 The following node types are used to completely describe a thermal management 19 system in devicetree: 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 24 25 This binding describes the thermal-zones. 26 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. 32 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. 39 40properties: 41 $nodename: 42 const: thermal-zones 43 description: 44 A /thermal-zones node is required in order to use the thermal framework to 45 manage input from the various thermal zones in the system in order to 46 mitigate thermal overload conditions. It does not represent a real device 47 in the system, but acts as a container to link a thermal sensor device, 48 platform-data regarding temperature thresholds and the mitigation actions 49 to take when the temperature crosses those thresholds. 50 51patternProperties: 52 "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$": 53 type: object 54 description: 55 Each thermal zone node contains information about how frequently it 56 must be checked, the sensor responsible for reporting temperature for 57 this zone, one sub-node containing the various trip points for this 58 zone and one sub-node containing all the zone cooling-maps. 59 60 properties: 61 polling-delay: 62 $ref: /schemas/types.yaml#/definitions/uint32 63 description: 64 The maximum number of milliseconds to wait between polls when 65 checking this thermal zone. Setting this to 0 disables the polling 66 timers setup by the thermal framework and assumes that the thermal 67 sensors in this zone support interrupts. 68 69 polling-delay-passive: 70 $ref: /schemas/types.yaml#/definitions/uint32 71 description: 72 The maximum number of milliseconds to wait between polls when 73 checking this thermal zone while doing passive cooling. Setting 74 this to 0 disables the polling timers setup by the thermal 75 framework and assumes that the thermal sensors in this zone 76 support interrupts. 77 78 thermal-sensors: 79 $ref: /schemas/types.yaml#/definitions/phandle-array 80 maxItems: 1 81 description: 82 The thermal sensor phandle and sensor specifier used to monitor this 83 thermal zone. 84 85 coefficients: 86 $ref: /schemas/types.yaml#/definitions/uint32-array 87 description: 88 An array of integers containing the coefficients of a linear equation 89 that binds all the sensors listed in this thermal zone. 90 91 The linear equation used is as follows, 92 z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn 93 where c0, c1, .., cn are the coefficients. 94 95 Coefficients default to 1 in case this property is not specified. The 96 coefficients are ordered and are matched with sensors by means of the 97 sensor ID. Additional coefficients are interpreted as constant offset. 98 99 sustainable-power: 100 $ref: /schemas/types.yaml#/definitions/uint32 101 description: 102 An estimate of the sustainable power (in mW) that this thermal zone 103 can dissipate at the desired control temperature. For reference, the 104 sustainable power of a 4-inch phone is typically 2000mW, while on a 105 10-inch tablet is around 4500mW. 106 107 trips: 108 type: object 109 description: 110 This node describes a set of points in the temperature domain at 111 which the thermal framework needs to take action. The actions to 112 be taken are defined in another node called cooling-maps. 113 114 patternProperties: 115 "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$": 116 type: object 117 118 properties: 119 temperature: 120 $ref: /schemas/types.yaml#/definitions/int32 121 minimum: -273000 122 maximum: 200000 123 description: 124 An integer expressing the trip temperature in millicelsius. 125 126 hysteresis: 127 $ref: /schemas/types.yaml#/definitions/uint32 128 description: 129 An unsigned integer expressing the hysteresis delta with 130 respect to the trip temperature property above, also in 131 millicelsius. Any cooling action initiated by the framework is 132 maintained until the temperature falls below 133 (trip temperature - hysteresis). This potentially prevents a 134 situation where the trip gets constantly triggered soon after 135 cooling action is removed. 136 137 type: 138 $ref: /schemas/types.yaml#/definitions/string 139 enum: 140 - active # enable active cooling e.g. fans 141 - passive # enable passive cooling e.g. throttling cpu 142 - hot # send notification to driver 143 - critical # send notification to driver, trigger shutdown 144 description: | 145 There are four valid trip types: active, passive, hot, 146 critical. 147 148 The critical trip type is used to set the maximum 149 temperature threshold above which the HW becomes 150 unstable and underlying firmware might even trigger a 151 reboot. Hitting the critical threshold triggers a system 152 shutdown. 153 154 The hot trip type can be used to send a notification to 155 the thermal driver (if a .notify callback is registered). 156 The action to be taken is left to the driver. 157 158 The passive trip type can be used to slow down HW e.g. run 159 the CPU, GPU, bus at a lower frequency. 160 161 The active trip type can be used to control other HW to 162 help in cooling e.g. fans can be sped up or slowed down 163 164 required: 165 - temperature 166 - hysteresis 167 - type 168 additionalProperties: false 169 170 additionalProperties: false 171 172 cooling-maps: 173 type: object 174 description: 175 This node describes the action to be taken when a thermal zone 176 crosses one of the temperature thresholds described in the trips 177 node. The action takes the form of a mapping relation between a 178 trip and the target cooling device state. 179 180 patternProperties: 181 "^map[-a-zA-Z0-9]*$": 182 type: object 183 184 properties: 185 trip: 186 $ref: /schemas/types.yaml#/definitions/phandle 187 description: 188 A phandle of a trip point node within this thermal zone. 189 190 cooling-device: 191 $ref: /schemas/types.yaml#/definitions/phandle-array 192 description: 193 A list of cooling device phandles along with the minimum 194 and maximum cooling state specifiers for each cooling 195 device. Using the THERMAL_NO_LIMIT (-1UL) constant in the 196 cooling-device phandle limit specifier lets the framework 197 use the minimum and maximum cooling state for that cooling 198 device automatically. 199 200 contribution: 201 $ref: /schemas/types.yaml#/definitions/uint32 202 description: 203 The cooling contribution to the thermal zone of the referred 204 cooling device at the referred trip point. The contribution is 205 a ratio of the sum of all cooling contributions within a 206 thermal zone. 207 208 required: 209 - trip 210 - cooling-device 211 additionalProperties: false 212 213 required: 214 - polling-delay 215 - polling-delay-passive 216 - thermal-sensors 217 218 additionalProperties: false 219 220additionalProperties: false 221 222examples: 223 - | 224 #include <dt-bindings/interrupt-controller/arm-gic.h> 225 #include <dt-bindings/thermal/thermal.h> 226 227 // Example 1: SDM845 TSENS 228 soc { 229 #address-cells = <2>; 230 #size-cells = <2>; 231 232 /* ... */ 233 234 tsens0: thermal-sensor@c263000 { 235 compatible = "qcom,sdm845-tsens", "qcom,tsens-v2"; 236 reg = <0 0x0c263000 0 0x1ff>, /* TM */ 237 <0 0x0c222000 0 0x1ff>; /* SROT */ 238 #qcom,sensors = <13>; 239 interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>, 240 <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>; 241 interrupt-names = "uplow", "critical"; 242 #thermal-sensor-cells = <1>; 243 }; 244 245 tsens1: thermal-sensor@c265000 { 246 compatible = "qcom,sdm845-tsens", "qcom,tsens-v2"; 247 reg = <0 0x0c265000 0 0x1ff>, /* TM */ 248 <0 0x0c223000 0 0x1ff>; /* SROT */ 249 #qcom,sensors = <8>; 250 interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>, 251 <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>; 252 interrupt-names = "uplow", "critical"; 253 #thermal-sensor-cells = <1>; 254 }; 255 }; 256 257 /* ... */ 258 259 thermal-zones { 260 cpu0-thermal { 261 polling-delay-passive = <250>; 262 polling-delay = <1000>; 263 264 thermal-sensors = <&tsens0 1>; 265 266 trips { 267 cpu0_alert0: trip-point0 { 268 temperature = <90000>; 269 hysteresis = <2000>; 270 type = "passive"; 271 }; 272 273 cpu0_alert1: trip-point1 { 274 temperature = <95000>; 275 hysteresis = <2000>; 276 type = "passive"; 277 }; 278 279 cpu0_crit: cpu_crit { 280 temperature = <110000>; 281 hysteresis = <1000>; 282 type = "critical"; 283 }; 284 }; 285 286 cooling-maps { 287 map0 { 288 trip = <&cpu0_alert0>; 289 /* Corresponds to 1400MHz in OPP table */ 290 cooling-device = <&CPU0 3 3>, <&CPU1 3 3>, 291 <&CPU2 3 3>, <&CPU3 3 3>; 292 }; 293 294 map1 { 295 trip = <&cpu0_alert1>; 296 /* Corresponds to 1000MHz in OPP table */ 297 cooling-device = <&CPU0 5 5>, <&CPU1 5 5>, 298 <&CPU2 5 5>, <&CPU3 5 5>; 299 }; 300 }; 301 }; 302 303 /* ... */ 304 305 cluster0-thermal { 306 polling-delay-passive = <250>; 307 polling-delay = <1000>; 308 309 thermal-sensors = <&tsens0 5>; 310 311 trips { 312 cluster0_alert0: trip-point0 { 313 temperature = <90000>; 314 hysteresis = <2000>; 315 type = "hot"; 316 }; 317 cluster0_crit: cluster0_crit { 318 temperature = <110000>; 319 hysteresis = <2000>; 320 type = "critical"; 321 }; 322 }; 323 }; 324 325 /* ... */ 326 327 gpu-top-thermal { 328 polling-delay-passive = <250>; 329 polling-delay = <1000>; 330 331 thermal-sensors = <&tsens0 11>; 332 333 trips { 334 gpu1_alert0: trip-point0 { 335 temperature = <90000>; 336 hysteresis = <2000>; 337 type = "hot"; 338 }; 339 }; 340 }; 341 }; 342... 343