Documentation/devicetree/bindings/thermal/thermal-cooling-devices.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-cooling-devices.yaml#
   6 $schema: http://devicetree.org/meta-schemas/core.yaml#
   7
   8 title: Thermal cooling device 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 overload.
  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 cooling devices.
  26
  27   There are essentially two ways to provide control on power dissipation:
  28     - Passive cooling: by means of regulating device performance. A typical
  29       passive cooling mechanism is a CPU that has dynamic voltage and frequency
  30       scaling (DVFS), and uses lower frequencies as cooling states.
  31     - Active cooling: by means of activating devices in order to remove the
  32       dissipated heat, e.g. regulating fan speeds.
  33
  34   Any cooling device has a range of cooling states (i.e. different levels of
  35   heat dissipation). They also have a way to determine the state of cooling in
  36   which the device is. For example, a fan's cooling states correspond to the
  37   different fan speeds possible. Cooling states are referred to by single
  38   unsigned integers, where larger numbers mean greater heat dissipation. The
  39   precise set of cooling states associated with a device should be defined in
  40   a particular device's binding.
  41
  42 select: true
  43
  44 properties:
  45   "#cooling-cells":
  46     description:
  47       Must be 2, in order to specify minimum and maximum cooling state used in
  48       the cooling-maps reference. The first cell is the minimum cooling state
  49       and the second cell is the maximum cooling state requested.
  50     const: 2
  51
  52 additionalProperties: true
  53
  54 examples:
  55   - |
  56     #include <dt-bindings/interrupt-controller/arm-gic.h>
  57     #include <dt-bindings/thermal/thermal.h>
  58
  59     // Example 1: Cpufreq cooling device on CPU0
  60     cpus {
  61             #address-cells = <2>;
  62             #size-cells = <0>;
  63
  64             CPU0: cpu@0 {
  65                     device_type = "cpu";
  66                     compatible = "qcom,kryo385";
  67                     reg = <0x0 0x0>;
  68                     enable-method = "psci";
  69                     cpu-idle-states = <&LITTLE_CPU_SLEEP_0
  70                                        &LITTLE_CPU_SLEEP_1
  71                                        &CLUSTER_SLEEP_0>;
  72                     capacity-dmips-mhz = <607>;
  73                     dynamic-power-coefficient = <100>;
  74                     qcom,freq-domain = <&cpufreq_hw 0>;
  75                     #cooling-cells = <2>;
  76                     next-level-cache = <&L2_0>;
  77                     L2_0: l2-cache {
  78                             compatible = "cache";
  79                             next-level-cache = <&L3_0>;
  80                             L3_0: l3-cache {
  81                                     compatible = "cache";
  82                             };
  83                     };
  84           };
  85
  86           /* ... */
  87
  88     };
  89
  90     /* ... */
  91
  92     thermal-zones {
  93             cpu0-thermal {
  94                     polling-delay-passive = <250>;
  95                     polling-delay = <1000>;
  96
  97                     thermal-sensors = <&tsens0 1>;
  98
  99                     trips {
 100                             cpu0_alert0: trip-point0 {
 101                                     temperature = <90000>;
 102                                     hysteresis = <2000>;
 103                                     type = "passive";
 104                             };
 105                     };
 106
 107                     cooling-maps {
 108                             map0 {
 109                                     trip = <&cpu0_alert0>;
 110                                     /* Corresponds to 1000MHz in OPP table */
 111                                     cooling-device = <&CPU0 5 5>;
 112                             };
 113                     };
 114             };
 115
 116             /* ... */
 117     };
 118 ...