Documentation/devicetree/bindings/thermal/thermal-zones.yaml

   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
   8 title: Thermal zone binding
   9
  10 maintainers:
  11   - Amit Kucheria <amitk@kernel.org>
  12
  13 description: |
  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
  40 properties:
  41   $nodename:
  42     const: thermal-zones
  43     description:
  44       A /thermal-zones node is required in order to use the thermal framework to
  45       manage input from the various thermal zones in the system in order to
  46       mitigate thermal overload conditions. It does not represent a real device
  47       in the system, but acts as a container to link a thermal sensor device,
  48       platform-data regarding temperature thresholds and the mitigation actions
  49       to take when the temperature crosses those thresholds.
  50
  51 patternProperties:
  52   "^[a-zA-Z][a-zA-Z0-9\\-]{1,12}-thermal$":
  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                 minimum: 0
 203                 maximum: 100
 204                 description:
 205                   The percentage contribution of the cooling devices at the
 206                   specific trip temperature referenced in this map
 207                   to this thermal zone
 208
 209             required:
 210               - trip
 211               - cooling-device
 212             additionalProperties: false
 213
 214     required:
 215       - polling-delay
 216       - polling-delay-passive
 217       - thermal-sensors
 218
 219     additionalProperties: false
 220
 221 additionalProperties: false
 222
 223 examples:
 224   - |
 225     #include <dt-bindings/interrupt-controller/arm-gic.h>
 226     #include <dt-bindings/thermal/thermal.h>
 227
 228     // Example 1: SDM845 TSENS
 229     soc {
 230             #address-cells = <2>;
 231             #size-cells = <2>;
 232
 233             /* ... */
 234
 235             tsens0: thermal-sensor@c263000 {
 236                     compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
 237                     reg = <0 0x0c263000 0 0x1ff>, /* TM */
 238                           <0 0x0c222000 0 0x1ff>; /* SROT */
 239                     #qcom,sensors = <13>;
 240                     interrupts = <GIC_SPI 506 IRQ_TYPE_LEVEL_HIGH>,
 241                                  <GIC_SPI 508 IRQ_TYPE_LEVEL_HIGH>;
 242                     interrupt-names = "uplow", "critical";
 243                     #thermal-sensor-cells = <1>;
 244             };
 245
 246             tsens1: thermal-sensor@c265000 {
 247                     compatible = "qcom,sdm845-tsens", "qcom,tsens-v2";
 248                     reg = <0 0x0c265000 0 0x1ff>, /* TM */
 249                           <0 0x0c223000 0 0x1ff>; /* SROT */
 250                     #qcom,sensors = <8>;
 251                     interrupts = <GIC_SPI 507 IRQ_TYPE_LEVEL_HIGH>,
 252                                  <GIC_SPI 509 IRQ_TYPE_LEVEL_HIGH>;
 253                     interrupt-names = "uplow", "critical";
 254                     #thermal-sensor-cells = <1>;
 255             };
 256     };
 257
 258     /* ... */
 259
 260     thermal-zones {
 261             cpu0-thermal {
 262                     polling-delay-passive = <250>;
 263                     polling-delay = <1000>;
 264
 265                     thermal-sensors = <&tsens0 1>;
 266
 267                     trips {
 268                             cpu0_alert0: trip-point0 {
 269                                     temperature = <90000>;
 270                                     hysteresis = <2000>;
 271                                     type = "passive";
 272                             };
 273
 274                             cpu0_alert1: trip-point1 {
 275                                     temperature = <95000>;
 276                                     hysteresis = <2000>;
 277                                     type = "passive";
 278                             };
 279
 280                             cpu0_crit: cpu_crit {
 281                                     temperature = <110000>;
 282                                     hysteresis = <1000>;
 283                                     type = "critical";
 284                             };
 285                     };
 286
 287                     cooling-maps {
 288                             map0 {
 289                                     trip = <&cpu0_alert0>;
 290                                     /* Corresponds to 1400MHz in OPP table */
 291                                     cooling-device = <&CPU0 3 3>, <&CPU1 3 3>,
 292                                                      <&CPU2 3 3>, <&CPU3 3 3>;
 293                             };
 294
 295                             map1 {
 296                                     trip = <&cpu0_alert1>;
 297                                     /* Corresponds to 1000MHz in OPP table */
 298                                     cooling-device = <&CPU0 5 5>, <&CPU1 5 5>,
 299                                                      <&CPU2 5 5>, <&CPU3 5 5>;
 300                             };
 301                     };
 302             };
 303
 304             /* ... */
 305
 306             cluster0-thermal {
 307                     polling-delay-passive = <250>;
 308                     polling-delay = <1000>;
 309
 310                     thermal-sensors = <&tsens0 5>;
 311
 312                     trips {
 313                             cluster0_alert0: trip-point0 {
 314                                     temperature = <90000>;
 315                                     hysteresis = <2000>;
 316                                     type = "hot";
 317                             };
 318                             cluster0_crit: cluster0_crit {
 319                                     temperature = <110000>;
 320                                     hysteresis = <2000>;
 321                                     type = "critical";
 322                             };
 323                     };
 324             };
 325
 326             /* ... */
 327
 328             gpu-top-thermal {
 329                     polling-delay-passive = <250>;
 330                     polling-delay = <1000>;
 331
 332                     thermal-sensors = <&tsens0 11>;
 333
 334                     trips {
 335                             gpu1_alert0: trip-point0 {
 336                                     temperature = <90000>;
 337                                     hysteresis = <2000>;
 338                                     type = "hot";
 339                             };
 340                     };
 341             };
 342     };
 343 ...