xref: /openbmc/linux/Documentation/devicetree/bindings/thermal/thermal-idle.yaml (revision 1e1129b65ef3f72dbccf24de56b700a181b45227)
1# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2# Copyright 2020 Linaro Ltd.
3%YAML 1.2
4---
5$id: http://devicetree.org/schemas/thermal/thermal-idle.yaml#
6$schema: http://devicetree.org/meta-schemas/core.yaml#
7
8title: Thermal idle cooling device binding
9
10maintainers:
11  - Daniel Lezcano <daniel.lezcano@linaro.org>
12
13description: |
14  The thermal idle cooling device allows the system to passively
15  mitigate the temperature on the device by injecting idle cycles,
16  forcing it to cool down.
17
18  This binding describes the thermal idle node.
19
20properties:
21  $nodename:
22    const: thermal-idle
23    description: |
24      A thermal-idle node describes the idle cooling device properties to
25      cool down efficiently the attached thermal zone.
26
27  '#cooling-cells':
28    const: 2
29    description: |
30      Must be 2, in order to specify minimum and maximum cooling state used in
31      the cooling-maps reference. The first cell is the minimum cooling state
32      and the second cell is the maximum cooling state requested.
33
34  duration-us:
35    description: |
36      The idle duration in microsecond the device should cool down.
37
38  exit-latency-us:
39    description: |
40      The exit latency constraint in microsecond for the injected idle state
41      for the device. It is the latency constraint to apply when selecting an
42      idle state from among all the present ones.
43
44required:
45  - '#cooling-cells'
46
47examples:
48  - |
49    #include <dt-bindings/thermal/thermal.h>
50
51    // Example: Combining idle cooling device on big CPUs with cpufreq cooling device
52    cpus {
53            #address-cells = <2>;
54            #size-cells = <0>;
55
56            /* ... */
57
58                 cpu_b0: cpu@100 {
59                         device_type = "cpu";
60                         compatible = "arm,cortex-a72";
61                         reg = <0x0 0x100>;
62                         enable-method = "psci";
63                         capacity-dmips-mhz = <1024>;
64                         dynamic-power-coefficient = <436>;
65                         #cooling-cells = <2>; /* min followed by max */
66                         cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
67                         thermal-idle {
68                                 #cooling-cells = <2>;
69                                 duration-us = <10000>;
70                                 exit-latency-us = <500>;
71                         };
72                };
73
74                cpu_b1: cpu@101 {
75                        device_type = "cpu";
76                        compatible = "arm,cortex-a72";
77                        reg = <0x0 0x101>;
78                        enable-method = "psci";
79                        capacity-dmips-mhz = <1024>;
80                        dynamic-power-coefficient = <436>;
81                        #cooling-cells = <2>; /* min followed by max */
82                        cpu-idle-states = <&CPU_SLEEP &CLUSTER_SLEEP>;
83                        thermal-idle {
84                                #cooling-cells = <2>;
85                                duration-us = <10000>;
86                                exit-latency-us = <500>;
87                        };
88                 };
89
90          /* ... */
91
92    };
93
94    /* ... */
95
96    thermal_zones {
97         cpu_thermal: cpu {
98                polling-delay-passive = <100>;
99                polling-delay = <1000>;
100
101                /* ... */
102
103                trips {
104                        cpu_alert0: cpu_alert0 {
105                                    temperature = <65000>;
106                                    hysteresis = <2000>;
107                                    type = "passive";
108                        };
109
110                        cpu_alert1: cpu_alert1 {
111                                    temperature = <70000>;
112                                    hysteresis = <2000>;
113                                    type = "passive";
114                        };
115
116                        cpu_alert2: cpu_alert2 {
117                                    temperature = <75000>;
118                                    hysteresis = <2000>;
119                                    type = "passive";
120                        };
121
122                        cpu_crit: cpu_crit {
123                                    temperature = <95000>;
124                                    hysteresis = <2000>;
125                                    type = "critical";
126                        };
127                };
128
129                cooling-maps {
130                        map0 {
131                             trip = <&cpu_alert1>;
132                             cooling-device = <&{/cpus/cpu@100/thermal-idle} 0 15 >,
133                                              <&{/cpus/cpu@101/thermal-idle} 0 15>;
134                        };
135
136                        map1 {
137                             trip = <&cpu_alert2>;
138                             cooling-device =
139                                        <&cpu_b0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
140                                        <&cpu_b1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
141                       };
142                };
143          };
144    };
145