arm64: dts: qcom: sm8550: add TRNG node
[linux-modified.git] / drivers / thermal / gov_bang_bang.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
4  *
5  *  Copyright (C) 2014 Peter Kaestle <peter@piie.net>
6  *
7  *  Based on step_wise.c with following Copyrights:
8  *  Copyright (C) 2012 Intel Corp
9  *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
10  */
11
12 #include <linux/thermal.h>
13
14 #include "thermal_core.h"
15
16 static int thermal_zone_trip_update(struct thermal_zone_device *tz,
17                                     const struct thermal_trip *trip)
18 {
19         int trip_index = thermal_zone_trip_id(tz, trip);
20         struct thermal_instance *instance;
21
22         if (!trip->hysteresis)
23                 dev_info_once(&tz->device,
24                               "Zero hysteresis value for thermal zone %s\n", tz->type);
25
26         dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
27                                 trip_index, trip->temperature, tz->temperature,
28                                 trip->hysteresis);
29
30         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
31                 if (instance->trip != trip)
32                         continue;
33
34                 /* in case fan is in initial state, switch the fan off */
35                 if (instance->target == THERMAL_NO_TARGET)
36                         instance->target = 0;
37
38                 /* in case fan is neither on nor off set the fan to active */
39                 if (instance->target != 0 && instance->target != 1) {
40                         pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",
41                                         instance->name, instance->target);
42                         instance->target = 1;
43                 }
44
45                 /*
46                  * enable fan when temperature exceeds trip_temp and disable
47                  * the fan in case it falls below trip_temp minus hysteresis
48                  */
49                 if (instance->target == 0 && tz->temperature >= trip->temperature)
50                         instance->target = 1;
51                 else if (instance->target == 1 &&
52                          tz->temperature <= trip->temperature - trip->hysteresis)
53                         instance->target = 0;
54
55                 dev_dbg(&instance->cdev->device, "target=%d\n",
56                                         (int)instance->target);
57
58                 mutex_lock(&instance->cdev->lock);
59                 instance->cdev->updated = false; /* cdev needs update */
60                 mutex_unlock(&instance->cdev->lock);
61         }
62
63         return 0;
64 }
65
66 /**
67  * bang_bang_control - controls devices associated with the given zone
68  * @tz: thermal_zone_device
69  * @trip: the trip point
70  *
71  * Regulation Logic: a two point regulation, deliver cooling state depending
72  * on the previous state shown in this diagram:
73  *
74  *                Fan:   OFF    ON
75  *
76  *                              |
77  *                              |
78  *          trip_temp:    +---->+
79  *                        |     |        ^
80  *                        |     |        |
81  *                        |     |   Temperature
82  * (trip_temp - hyst):    +<----+
83  *                        |
84  *                        |
85  *                        |
86  *
87  *   * If the fan is not running and temperature exceeds trip_temp, the fan
88  *     gets turned on.
89  *   * In case the fan is running, temperature must fall below
90  *     (trip_temp - hyst) so that the fan gets turned off again.
91  *
92  */
93 static int bang_bang_control(struct thermal_zone_device *tz,
94                              const struct thermal_trip *trip)
95 {
96         struct thermal_instance *instance;
97         int ret;
98
99         lockdep_assert_held(&tz->lock);
100
101         ret = thermal_zone_trip_update(tz, trip);
102         if (ret)
103                 return ret;
104
105         list_for_each_entry(instance, &tz->thermal_instances, tz_node)
106                 thermal_cdev_update(instance->cdev);
107
108         return 0;
109 }
110
111 static struct thermal_governor thermal_gov_bang_bang = {
112         .name           = "bang_bang",
113         .throttle       = bang_bang_control,
114 };
115 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);