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Thomas Gleixner50acfb22019-05-29 07:18:00 -07001// SPDX-License-Identifier: GPL-2.0-only
Peter Feuerere4dbf982014-07-22 17:37:13 +02002/*
3 * gov_bang_bang.c - A simple thermal throttling governor using hysteresis
4 *
Peter Kaestled3f5b732019-10-19 00:59:36 +02005 * Copyright (C) 2014 Peter Kaestle <peter@piie.net>
Peter Feuerere4dbf982014-07-22 17:37:13 +02006 *
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>
Peter Feuerere4dbf982014-07-22 17:37:13 +020010 */
11
12#include <linux/thermal.h>
13
14#include "thermal_core.h"
15
Rafael J. Wysocki8c35b1f2023-10-12 20:34:50 +020016static int thermal_zone_trip_update(struct thermal_zone_device *tz,
17 const struct thermal_trip *trip)
Peter Feuerere4dbf982014-07-22 17:37:13 +020018{
Rafael J. Wysocki8c35b1f2023-10-12 20:34:50 +020019 int trip_index = thermal_zone_trip_id(tz, trip);
Peter Feuerere4dbf982014-07-22 17:37:13 +020020 struct thermal_instance *instance;
21
Rafael J. Wysocki2c7b4bf2023-09-21 19:52:44 +020022 if (!trip->hysteresis)
Daniel Lezcano7f725a22022-10-03 11:25:37 +020023 dev_info_once(&tz->device,
24 "Zero hysteresis value for thermal zone %s\n", tz->type);
Peter Feuerere4dbf982014-07-22 17:37:13 +020025
Sascha Hauer17e83512015-07-24 08:12:54 +020026 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
Rafael J. Wysocki2c7b4bf2023-09-21 19:52:44 +020027 trip_index, trip->temperature, tz->temperature,
28 trip->hysteresis);
Peter Feuerere4dbf982014-07-22 17:37:13 +020029
Peter Feuerere4dbf982014-07-22 17:37:13 +020030 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
Rafael J. Wysocki2c7b4bf2023-09-21 19:52:44 +020031 if (instance->trip != trip)
Peter Feuerere4dbf982014-07-22 17:37:13 +020032 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 */
Rafael J. Wysocki2c7b4bf2023-09-21 19:52:44 +020049 if (instance->target == 0 && tz->temperature >= trip->temperature)
Peter Feuerere4dbf982014-07-22 17:37:13 +020050 instance->target = 1;
51 else if (instance->target == 1 &&
Rafael J. Wysocki2c7b4bf2023-09-21 19:52:44 +020052 tz->temperature <= trip->temperature - trip->hysteresis)
Peter Feuerere4dbf982014-07-22 17:37:13 +020053 instance->target = 0;
54
55 dev_dbg(&instance->cdev->device, "target=%d\n",
56 (int)instance->target);
57
Michele Di Giorgiod0b73062016-06-02 15:25:31 +010058 mutex_lock(&instance->cdev->lock);
Peter Feuerere4dbf982014-07-22 17:37:13 +020059 instance->cdev->updated = false; /* cdev needs update */
Michele Di Giorgiod0b73062016-06-02 15:25:31 +010060 mutex_unlock(&instance->cdev->lock);
Peter Feuerere4dbf982014-07-22 17:37:13 +020061 }
Daniel Lezcano7f725a22022-10-03 11:25:37 +020062
63 return 0;
Peter Feuerere4dbf982014-07-22 17:37:13 +020064}
65
66/**
67 * bang_bang_control - controls devices associated with the given zone
Amit Kucheria53d256e2019-11-20 21:15:12 +053068 * @tz: thermal_zone_device
69 * @trip: the trip point
Peter Feuerere4dbf982014-07-22 17:37:13 +020070 *
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 */
Rafael J. Wysocki8c35b1f2023-10-12 20:34:50 +020093static int bang_bang_control(struct thermal_zone_device *tz,
94 const struct thermal_trip *trip)
Peter Feuerere4dbf982014-07-22 17:37:13 +020095{
96 struct thermal_instance *instance;
Daniel Lezcano7f725a22022-10-03 11:25:37 +020097 int ret;
Peter Feuerere4dbf982014-07-22 17:37:13 +020098
Daniel Lezcano670a5e32022-08-05 17:38:33 +020099 lockdep_assert_held(&tz->lock);
Peter Feuerere4dbf982014-07-22 17:37:13 +0200100
Daniel Lezcano7f725a22022-10-03 11:25:37 +0200101 ret = thermal_zone_trip_update(tz, trip);
102 if (ret)
103 return ret;
Daniel Lezcano63561fe2022-08-05 17:38:32 +0200104
Peter Feuerere4dbf982014-07-22 17:37:13 +0200105 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
106 thermal_cdev_update(instance->cdev);
107
Peter Feuerere4dbf982014-07-22 17:37:13 +0200108 return 0;
109}
110
111static struct thermal_governor thermal_gov_bang_bang = {
112 .name = "bang_bang",
113 .throttle = bang_bang_control,
114};
Daniel Lezcano57c5b2e2019-06-12 22:13:25 +0200115THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);