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 9 10maintainers: 11 - Daniel Lezcano <daniel.lezcano@linaro.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 critical-action: 79 $ref: /schemas/types.yaml#/definitions/string 80 description: | 81 The action the OS should perform after the critical temperature is reached. 82 By default the system will shutdown as a safe action to prevent damage 83 to the hardware, if the property is not set. 84 The shutdown action should be always the default and preferred one. 85 Choose 'reboot' with care, as the hardware may be in thermal stress, 86 thus leading to infinite reboots that may cause damage to the hardware. 87 Make sure the firmware/bootloader will act as the last resort and take 88 over the thermal control. 89 90 enum: 91 - shutdown 92 - reboot 93 94 thermal-sensors: 95 $ref: /schemas/types.yaml#/definitions/phandle-array 96 maxItems: 1 97 description: 98 The thermal sensor phandle and sensor specifier used to monitor this 99 thermal zone. 100 101 coefficients: 102 $ref: /schemas/types.yaml#/definitions/uint32-array 103 description: 104 An array of integers containing the coefficients of a linear equation 105 that binds all the sensors listed in this thermal zone. 106 107 The linear equation used is as follows, 108 z = c0 * x0 + c1 * x1 + ... + c(n-1) * x(n-1) + cn 109 where c0, c1, .., cn are the coefficients. 110 111 Coefficients default to 1 in case this property is not specified. The 112 coefficients are ordered and are matched with sensors by means of the 113 sensor ID. Additional coefficients are interpreted as constant offset. 114 115 sustainable-power: 116 $ref: /schemas/types.yaml#/definitions/uint32 117 description: 118 An estimate of the sustainable power (in mW) that this thermal zone 119 can dissipate at the desired control temperature. For reference, the 120 sustainable power of a 4-inch phone is typically 2000mW, while on a 121 10-inch tablet is around 4500mW. 122 123 trips: 124 type: object 125 description: 126 This node describes a set of points in the temperature domain at 127 which the thermal framework needs to take action. The actions to 128 be taken are defined in another node called cooling-maps. 129 130 patternProperties: 131 "^[a-zA-Z][a-zA-Z0-9\\-_]{0,63}$": 132 type: object 133 134 properties: 135 temperature: 136 $ref: /schemas/types.yaml#/definitions/int32 137 minimum: -273000 138 maximum: 200000 139 description: 140 An integer expressing the trip temperature in millicelsius. 141 142 hysteresis: 143 $ref: /schemas/types.yaml#/definitions/uint32 144 description: 145 An unsigned integer expressing the hysteresis delta with 146 respect to the trip temperature property above, also in 147 millicelsius. Any cooling action initiated by the framework is 148 maintained until the temperature falls below 149 (trip temperature - hysteresis). This potentially prevents a 150 situation where the trip gets constantly triggered soon after 151 cooling action is removed. 152 153 type: 154 $ref: /schemas/types.yaml#/definitions/string 155 enum: 156 - active # enable active cooling e.g. fans 157 - passive # enable passive cooling e.g. throttling cpu 158 - hot # send notification to driver 159 - critical # send notification to driver, trigger shutdown 160 description: | 161 There are four valid trip types: active, passive, hot, 162 critical. 163 164 The critical trip type is used to set the maximum 165 temperature threshold above which the HW becomes 166 unstable and underlying firmware might even trigger a 167 reboot. Hitting the critical threshold triggers a system 168 shutdown. 169 170 The hot trip type can be used to send a notification to 171 the thermal driver (if a .notify callback is registered). 172 The action to be taken is left to the driver. 173 174 The passive trip type can be used to slow down HW e.g. run 175 the CPU, GPU, bus at a lower frequency. 176 177 The active trip type can be used to control other HW to 178 help in cooling e.g. fans can be sped up or slowed down 179 180 required: 181 - temperature 182 - hysteresis 183 - type 184 additionalProperties: false 185 186 additionalProperties: false 187 188 cooling-maps: 189 type: object 190 additionalProperties: false 191 description: 192 This node describes the action to be taken when a thermal zone 193 crosses one of the temperature thresholds described in the trips 194 node. The action takes the form of a mapping relation between a 195 trip and the target cooling device state. 196 197 patternProperties: 198 "^map[-a-zA-Z0-9]*$": 199 type: object 200 201 properties: 202 trip: 203 $ref: /schemas/types.yaml#/definitions/phandle 204 description: 205 A phandle of a trip point node within this thermal zone. 206 207 cooling-device: 208 $ref: /schemas/types.yaml#/definitions/phandle-array 209 description: 210 A list of cooling device phandles along with the minimum 211 and maximum cooling state specifiers for each cooling 212 device. Using the THERMAL_NO_LIMIT (-1UL) constant in the 213 cooling-device phandle limit specifier lets the framework 214 use the minimum and maximum cooling state for that cooling 215 device automatically. 216 217 contribution: 218 $ref: /schemas/types.yaml#/definitions/uint32 219 description: 220 The cooling contribution to the thermal zone of the referred 221 cooling device at the referred trip point. The contribution is 222 a ratio of the sum of all cooling contributions within a 223 thermal zone. 224 225 required: 226 - trip 227 - cooling-device 228 additionalProperties: false 229 230 required: 231 - polling-delay 232 - polling-delay-passive 233 - thermal-sensors 234 - trips 235 236 additionalProperties: false 237 238additionalProperties: false 239 240examples: 241 - | 242 #include <dt-bindings/interrupt-controller/arm-gic.h> 243 #include <dt-bindings/thermal/thermal.h> 244 245 // Example 1: SDM845 TSENS 246 soc { 247 #address-cells = <2>; 248 #size-cells = <2>; 249 250 /* ... */ 251 252 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>; 261 }; 262 263 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 */ 267 #qcom,sensors = <8>; 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>; 272 }; 273 }; 274 275 /* ... */ 276 277 thermal-zones { 278 cpu0-thermal { 279 polling-delay-passive = <250>; 280 polling-delay = <1000>; 281 282 thermal-sensors = <&tsens0 1>; 283 284 trips { 285 cpu0_alert0: trip-point0 { 286 temperature = <90000>; 287 hysteresis = <2000>; 288 type = "passive"; 289 }; 290 291 cpu0_alert1: trip-point1 { 292 temperature = <95000>; 293 hysteresis = <2000>; 294 type = "passive"; 295 }; 296 297 cpu0_crit: cpu_crit { 298 temperature = <110000>; 299 hysteresis = <1000>; 300 type = "critical"; 301 }; 302 }; 303 304 cooling-maps { 305 map0 { 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>; 310 }; 311 312 map1 { 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>; 317 }; 318 }; 319 }; 320 321 /* ... */ 322 323 cluster0-thermal { 324 polling-delay-passive = <250>; 325 polling-delay = <1000>; 326 327 thermal-sensors = <&tsens0 5>; 328 329 trips { 330 cluster0_alert0: trip-point0 { 331 temperature = <90000>; 332 hysteresis = <2000>; 333 type = "hot"; 334 }; 335 cluster0_crit: cluster0_crit { 336 temperature = <110000>; 337 hysteresis = <2000>; 338 type = "critical"; 339 }; 340 }; 341 }; 342 343 /* ... */ 344 345 gpu-top-thermal { 346 polling-delay-passive = <250>; 347 polling-delay = <1000>; 348 349 thermal-sensors = <&tsens0 11>; 350 351 trips { 352 gpu1_alert0: trip-point0 { 353 temperature = <90000>; 354 hysteresis = <2000>; 355 type = "hot"; 356 }; 357 }; 358 }; 359 }; 360... 361