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
bang_bang_set_instance_target(struct thermal_instance * instance,unsigned int target)16 static void bang_bang_set_instance_target(struct thermal_instance *instance,
17 unsigned int target)
18 {
19 if (instance->target != 0 && instance->target != 1 &&
20 instance->target != THERMAL_NO_TARGET)
21 pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n",
22 instance->target, instance->name);
23
24 /*
25 * Enable the fan when the trip is crossed on the way up and disable it
26 * when the trip is crossed on the way down.
27 */
28 instance->target = target;
29 instance->initialized = true;
30
31 dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target);
32
33 mutex_lock(&instance->cdev->lock);
34 __thermal_cdev_update(instance->cdev);
35 mutex_unlock(&instance->cdev->lock);
36 }
37
38 /**
39 * bang_bang_control - controls devices associated with the given zone
40 * @tz: thermal_zone_device
41 * @trip: the trip point
42 * @crossed_up: whether or not the trip has been crossed on the way up
43 *
44 * Regulation Logic: a two point regulation, deliver cooling state depending
45 * on the previous state shown in this diagram:
46 *
47 * Fan: OFF ON
48 *
49 * |
50 * |
51 * trip_temp: +---->+
52 * | | ^
53 * | | |
54 * | | Temperature
55 * (trip_temp - hyst): +<----+
56 * |
57 * |
58 * |
59 *
60 * * If the fan is not running and temperature exceeds trip_temp, the fan
61 * gets turned on.
62 * * In case the fan is running, temperature must fall below
63 * (trip_temp - hyst) so that the fan gets turned off again.
64 *
65 */
bang_bang_control(struct thermal_zone_device * tz,const struct thermal_trip * trip,bool crossed_up)66 static void bang_bang_control(struct thermal_zone_device *tz,
67 const struct thermal_trip *trip,
68 bool crossed_up)
69 {
70 const struct thermal_trip_desc *td = trip_to_trip_desc(trip);
71 struct thermal_instance *instance;
72
73 lockdep_assert_held(&tz->lock);
74
75 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
76 thermal_zone_trip_id(tz, trip), trip->temperature,
77 tz->temperature, trip->hysteresis);
78
79 list_for_each_entry(instance, &td->thermal_instances, trip_node)
80 bang_bang_set_instance_target(instance, crossed_up);
81 }
82
bang_bang_manage(struct thermal_zone_device * tz)83 static void bang_bang_manage(struct thermal_zone_device *tz)
84 {
85 const struct thermal_trip_desc *td;
86 struct thermal_instance *instance;
87
88 /* If the code below has run already, nothing needs to be done. */
89 if (tz->governor_data)
90 return;
91
92 for_each_trip_desc(tz, td) {
93 const struct thermal_trip *trip = &td->trip;
94 bool turn_on;
95
96 if (trip->temperature == THERMAL_TEMP_INVALID ||
97 trip->type == THERMAL_TRIP_CRITICAL ||
98 trip->type == THERMAL_TRIP_HOT)
99 continue;
100
101 /*
102 * Adjust the target states for uninitialized thermal instances
103 * to the thermal zone temperature and the trip point threshold.
104 */
105 turn_on = tz->temperature >= td->threshold;
106 list_for_each_entry(instance, &td->thermal_instances, trip_node) {
107 if (!instance->initialized)
108 bang_bang_set_instance_target(instance, turn_on);
109 }
110 }
111
112 tz->governor_data = (void *)true;
113 }
114
bang_bang_update_tz(struct thermal_zone_device * tz,enum thermal_notify_event reason)115 static void bang_bang_update_tz(struct thermal_zone_device *tz,
116 enum thermal_notify_event reason)
117 {
118 /*
119 * Let bang_bang_manage() know that it needs to walk trips after binding
120 * a new cdev and after system resume.
121 */
122 if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME)
123 tz->governor_data = NULL;
124 }
125
126 static struct thermal_governor thermal_gov_bang_bang = {
127 .name = "bang_bang",
128 .trip_crossed = bang_bang_control,
129 .manage = bang_bang_manage,
130 .update_tz = bang_bang_update_tz,
131 };
132 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);
133