Root/drivers/thermal/step_wise.c

1/*
2 * step_wise.c - A step-by-step Thermal throttling governor
3 *
4 * Copyright (C) 2012 Intel Corp
5 * Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
6 *
7 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; version 2 of the License.
12 *
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License along
19 * with this program; if not, write to the Free Software Foundation, Inc.,
20 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
21 *
22 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
23 */
24
25#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26
27#include <linux/module.h>
28#include <linux/thermal.h>
29
30#include "thermal_core.h"
31
32/*
33 * If the temperature is higher than a trip point,
34 * a. if the trend is THERMAL_TREND_RAISING, use higher cooling
35 * state for this trip point
36 * b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
37 * state for this trip point
38 * c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
39 * for this trip point
40 * d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
41 * for this trip point
42 * If the temperature is lower than a trip point,
43 * a. if the trend is THERMAL_TREND_RAISING, do nothing
44 * b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
45 * state for this trip point, if the cooling state already
46 * equals lower limit, deactivate the thermal instance
47 * c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
48 * d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
49 * if the cooling state already equals lower limit,
50 * deactive the thermal instance
51 */
52static unsigned long get_target_state(struct thermal_instance *instance,
53                enum thermal_trend trend, bool throttle)
54{
55    struct thermal_cooling_device *cdev = instance->cdev;
56    unsigned long cur_state;
57
58    cdev->ops->get_cur_state(cdev, &cur_state);
59
60    switch (trend) {
61    case THERMAL_TREND_RAISING:
62        if (throttle)
63            cur_state = cur_state < instance->upper ?
64                    (cur_state + 1) : instance->upper;
65        break;
66    case THERMAL_TREND_RAISE_FULL:
67        if (throttle)
68            cur_state = instance->upper;
69        break;
70    case THERMAL_TREND_DROPPING:
71        if (cur_state == instance->lower) {
72            if (!throttle)
73                cur_state = -1;
74        } else
75            cur_state -= 1;
76        break;
77    case THERMAL_TREND_DROP_FULL:
78        if (cur_state == instance->lower) {
79            if (!throttle)
80                cur_state = -1;
81        } else
82            cur_state = instance->lower;
83        break;
84    default:
85        break;
86    }
87
88    return cur_state;
89}
90
91static void update_passive_instance(struct thermal_zone_device *tz,
92                enum thermal_trip_type type, int value)
93{
94    /*
95     * If value is +1, activate a passive instance.
96     * If value is -1, deactivate a passive instance.
97     */
98    if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
99        tz->passive += value;
100}
101
102static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
103{
104    long trip_temp;
105    enum thermal_trip_type trip_type;
106    enum thermal_trend trend;
107    struct thermal_instance *instance;
108    bool throttle = false;
109    int old_target;
110
111    if (trip == THERMAL_TRIPS_NONE) {
112        trip_temp = tz->forced_passive;
113        trip_type = THERMAL_TRIPS_NONE;
114    } else {
115        tz->ops->get_trip_temp(tz, trip, &trip_temp);
116        tz->ops->get_trip_type(tz, trip, &trip_type);
117    }
118
119    trend = get_tz_trend(tz, trip);
120
121    if (tz->temperature >= trip_temp)
122        throttle = true;
123
124    mutex_lock(&tz->lock);
125
126    list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
127        if (instance->trip != trip)
128            continue;
129
130        old_target = instance->target;
131        instance->target = get_target_state(instance, trend, throttle);
132
133        /* Activate a passive thermal instance */
134        if (old_target == THERMAL_NO_TARGET &&
135            instance->target != THERMAL_NO_TARGET)
136            update_passive_instance(tz, trip_type, 1);
137        /* Deactivate a passive thermal instance */
138        else if (old_target != THERMAL_NO_TARGET &&
139            instance->target == THERMAL_NO_TARGET)
140            update_passive_instance(tz, trip_type, -1);
141
142
143        instance->cdev->updated = false; /* cdev needs update */
144    }
145
146    mutex_unlock(&tz->lock);
147}
148
149/**
150 * step_wise_throttle - throttles devices asscciated with the given zone
151 * @tz - thermal_zone_device
152 * @trip - the trip point
153 * @trip_type - type of the trip point
154 *
155 * Throttling Logic: This uses the trend of the thermal zone to throttle.
156 * If the thermal zone is 'heating up' this throttles all the cooling
157 * devices associated with the zone and its particular trip point, by one
158 * step. If the zone is 'cooling down' it brings back the performance of
159 * the devices by one step.
160 */
161static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
162{
163    struct thermal_instance *instance;
164
165    thermal_zone_trip_update(tz, trip);
166
167    if (tz->forced_passive)
168        thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
169
170    mutex_lock(&tz->lock);
171
172    list_for_each_entry(instance, &tz->thermal_instances, tz_node)
173        thermal_cdev_update(instance->cdev);
174
175    mutex_unlock(&tz->lock);
176
177    return 0;
178}
179
180static struct thermal_governor thermal_gov_step_wise = {
181    .name = "step_wise",
182    .throttle = step_wise_throttle,
183    .owner = THIS_MODULE,
184};
185
186static int __init thermal_gov_step_wise_init(void)
187{
188    return thermal_register_governor(&thermal_gov_step_wise);
189}
190
191static void __exit thermal_gov_step_wise_exit(void)
192{
193    thermal_unregister_governor(&thermal_gov_step_wise);
194}
195
196/* This should load after thermal framework */
197fs_initcall(thermal_gov_step_wise_init);
198module_exit(thermal_gov_step_wise_exit);
199
200MODULE_AUTHOR("Durgadoss R");
201MODULE_DESCRIPTION("A step-by-step thermal throttling governor");
202MODULE_LICENSE("GPL");
203

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