0001 # SPDX-License-Identifier: (GPL-2.0)
0002 # Copyright 2020 Linaro Ltd.
0003 %YAML 1.2
0004 ---
0005 $id: http://devicetree.org/schemas/thermal/thermal-cooling-devices.yaml#
0006 $schema: http://devicetree.org/meta-schemas/core.yaml#
0007
0008 title: Thermal cooling device binding
0009
0010 maintainers:
0011 - Amit Kucheria <amitk@kernel.org>
0012
0013 description: |
0014 Thermal management is achieved in devicetree by describing the sensor hardware
0015 and the software abstraction of cooling devices and thermal zones required to
0016 take appropriate action to mitigate thermal overload.
0017
0018 The following node types are used to completely describe a thermal management
0019 system in devicetree:
0020 - thermal-sensor: device that measures temperature, has SoC-specific bindings
0021 - cooling-device: device used to dissipate heat either passively or actively
0022 - thermal-zones: a container of the following node types used to describe all
0023 thermal data for the platform
0024
0025 This binding describes the cooling devices.
0026
0027 There are essentially two ways to provide control on power dissipation:
0028 - Passive cooling: by means of regulating device performance. A typical
0029 passive cooling mechanism is a CPU that has dynamic voltage and frequency
0030 scaling (DVFS), and uses lower frequencies as cooling states.
0031 - Active cooling: by means of activating devices in order to remove the
0032 dissipated heat, e.g. regulating fan speeds.
0033
0034 Any cooling device has a range of cooling states (i.e. different levels of
0035 heat dissipation). They also have a way to determine the state of cooling in
0036 which the device is. For example, a fan's cooling states correspond to the
0037 different fan speeds possible. Cooling states are referred to by single
0038 unsigned integers, where larger numbers mean greater heat dissipation. The
0039 precise set of cooling states associated with a device should be defined in
0040 a particular device's binding.
0041
0042 select: true
0043
0044 properties:
0045 "#cooling-cells":
0046 description:
0047 Must be 2, in order to specify minimum and maximum cooling state used in
0048 the cooling-maps reference. The first cell is the minimum cooling state
0049 and the second cell is the maximum cooling state requested.
0050 const: 2
0051
0052 additionalProperties: true
0053
0054 examples:
0055 - |
0056 #include <dt-bindings/interrupt-controller/arm-gic.h>
0057 #include <dt-bindings/thermal/thermal.h>
0058
0059 // Example 1: Cpufreq cooling device on CPU0
0060 cpus {
0061 #address-cells = <2>;
0062 #size-cells = <0>;
0063
0064 CPU0: cpu@0 {
0065 device_type = "cpu";
0066 compatible = "qcom,kryo385";
0067 reg = <0x0 0x0>;
0068 enable-method = "psci";
0069 cpu-idle-states = <&LITTLE_CPU_SLEEP_0>,
0070 <&LITTLE_CPU_SLEEP_1>,
0071 <&CLUSTER_SLEEP_0>;
0072 capacity-dmips-mhz = <607>;
0073 dynamic-power-coefficient = <100>;
0074 qcom,freq-domain = <&cpufreq_hw 0>;
0075 #cooling-cells = <2>;
0076 next-level-cache = <&L2_0>;
0077 L2_0: l2-cache {
0078 compatible = "cache";
0079 next-level-cache = <&L3_0>;
0080 L3_0: l3-cache {
0081 compatible = "cache";
0082 };
0083 };
0084 };
0085
0086 /* ... */
0087
0088 };
0089
0090 /* ... */
0091
0092 thermal-zones {
0093 cpu0-thermal {
0094 polling-delay-passive = <250>;
0095 polling-delay = <1000>;
0096
0097 thermal-sensors = <&tsens0 1>;
0098
0099 trips {
0100 cpu0_alert0: trip-point0 {
0101 temperature = <90000>;
0102 hysteresis = <2000>;
0103 type = "passive";
0104 };
0105 };
0106
0107 cooling-maps {
0108 map0 {
0109 trip = <&cpu0_alert0>;
0110 /* Corresponds to 1000MHz in OPP table */
0111 cooling-device = <&CPU0 5 5>;
0112 };
0113 };
0114 };
0115
0116 /* ... */
0117 };
0118 ...
