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 <[email protected]>
6 *
7 * Based on step_wise.c with following Copyrights:
8 * Copyright (C) 2012 Intel Corp
9 * Copyright (C) 2012 Durgadoss R <[email protected]>
10 *
11 * Regulation Logic: a two point regulation, deliver cooling state depending
12 * on the previous state shown in this diagram:
13 *
14 * Fan: OFF ON
15 *
16 * |
17 * |
18 * trip_temp: +---->+
19 * | | ^
20 * | | |
21 * | | Temperature
22 * (trip_temp - hyst): +<----+
23 * |
24 * |
25 * |
26 *
27 * * If the fan is not running and temperature exceeds trip_temp, the fan
28 * gets turned on.
29 * * In case the fan is running, temperature must fall below
30 * (trip_temp - hyst) so that the fan gets turned off again.
31 */
32
33 #include <linux/thermal.h>
34
35 #include "thermal_core.h"
36
bang_bang_set_instance_target(struct thermal_instance * instance,unsigned int target)37 static void bang_bang_set_instance_target(struct thermal_instance *instance,
38 unsigned int target)
39 {
40 if (instance->target != 0 && instance->target != 1 &&
41 instance->target != THERMAL_NO_TARGET)
42 pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n",
43 instance->target, instance->name);
44
45 /*
46 * Enable the fan when the trip is crossed on the way up and disable it
47 * when the trip is crossed on the way down.
48 */
49 instance->target = target;
50 instance->initialized = true;
51
52 dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target);
53
54 thermal_cdev_update_nocheck(instance->cdev);
55 }
56
57 /**
58 * bang_bang_trip_crossed - controls devices associated with the given zone
59 * @tz: thermal_zone_device
60 * @trip: the trip point
61 * @upward: whether or not the trip has been crossed on the way up
62 */
bang_bang_trip_crossed(struct thermal_zone_device * tz,const struct thermal_trip * trip,bool upward)63 static void bang_bang_trip_crossed(struct thermal_zone_device *tz,
64 const struct thermal_trip *trip,
65 bool upward)
66 {
67 const struct thermal_trip_desc *td = trip_to_trip_desc(trip);
68 struct thermal_instance *instance;
69
70 lockdep_assert_held(&tz->lock);
71
72 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
73 thermal_zone_trip_id(tz, trip), trip->temperature,
74 tz->temperature, trip->hysteresis);
75
76 list_for_each_entry(instance, &td->thermal_instances, trip_node)
77 bang_bang_set_instance_target(instance, upward);
78 }
79
bang_bang_manage(struct thermal_zone_device * tz)80 static void bang_bang_manage(struct thermal_zone_device *tz)
81 {
82 const struct thermal_trip_desc *td;
83 struct thermal_instance *instance;
84
85 /* If the code below has run already, nothing needs to be done. */
86 if (tz->governor_data)
87 return;
88
89 for_each_trip_desc(tz, td) {
90 const struct thermal_trip *trip = &td->trip;
91 bool turn_on;
92
93 if (trip->temperature == THERMAL_TEMP_INVALID ||
94 trip->type == THERMAL_TRIP_CRITICAL ||
95 trip->type == THERMAL_TRIP_HOT)
96 continue;
97
98 /*
99 * Adjust the target states for uninitialized thermal instances
100 * to the thermal zone temperature and the trip point threshold.
101 */
102 turn_on = tz->temperature >= td->threshold;
103 list_for_each_entry(instance, &td->thermal_instances, trip_node) {
104 if (!instance->initialized)
105 bang_bang_set_instance_target(instance, turn_on);
106 }
107 }
108
109 tz->governor_data = (void *)true;
110 }
111
bang_bang_update_tz(struct thermal_zone_device * tz,enum thermal_notify_event reason)112 static void bang_bang_update_tz(struct thermal_zone_device *tz,
113 enum thermal_notify_event reason)
114 {
115 /*
116 * Let bang_bang_manage() know that it needs to walk trips after binding
117 * a new cdev and after system resume.
118 */
119 if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME)
120 tz->governor_data = NULL;
121 }
122
123 static struct thermal_governor thermal_gov_bang_bang = {
124 .name = "bang_bang",
125 .trip_crossed = bang_bang_trip_crossed,
126 .manage = bang_bang_manage,
127 .update_tz = bang_bang_update_tz,
128 };
129 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);
130