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
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 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 ...
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.