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
  8title: Thermal cooling device
  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 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
 42select: true
 43
 44properties:
 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
 52additionalProperties: true
 53
 54examples:
 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                            cache-unified;
 80                            cache-level = <2>;
 81                            next-level-cache = <&L3_0>;
 82                            L3_0: l3-cache {
 83                                    compatible = "cache";
 84                                    cache-unified;
 85                                    cache-level = <3>;
 86                            };
 87                    };
 88          };
 89
 90          /* ... */
 91
 92    };
 93
 94    /* ... */
 95
 96    thermal-zones {
 97            cpu0-thermal {
 98                    polling-delay-passive = <250>;
 99                    polling-delay = <1000>;
100
101                    thermal-sensors = <&tsens0 1>;
102
103                    trips {
104                            cpu0_alert0: trip-point0 {
105                                    temperature = <90000>;
106                                    hysteresis = <2000>;
107                                    type = "passive";
108                            };
109                    };
110
111                    cooling-maps {
112                            map0 {
113                                    trip = <&cpu0_alert0>;
114                                    /* Corresponds to 1000MHz in OPP table */
115                                    cooling-device = <&CPU0 5 5>;
116                            };
117                    };
118            };
119
120            /* ... */
121    };
122...