Linux kernel mirror (for testing)
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linux
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#include <linux/thermal.h>
26
27#include "thermal_core.h"
28
29/*
30 * If the temperature is higher than a trip point,
31 * a. if the trend is THERMAL_TREND_RAISING, use higher cooling
32 * state for this trip point
33 * b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
34 * state for this trip point
35 * c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
36 * for this trip point
37 * d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
38 * for this trip point
39 * If the temperature is lower than a trip point,
40 * a. if the trend is THERMAL_TREND_RAISING, do nothing
41 * b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
42 * state for this trip point, if the cooling state already
43 * equals lower limit, deactivate the thermal instance
44 * c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
45 * d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
46 * if the cooling state already equals lower limit,
47 * deactive the thermal instance
48 */
49static unsigned long get_target_state(struct thermal_instance *instance,
50 enum thermal_trend trend, bool throttle)
51{
52 struct thermal_cooling_device *cdev = instance->cdev;
53 unsigned long cur_state;
54 unsigned long next_target;
55
56 /*
57 * We keep this instance the way it is by default.
58 * Otherwise, we use the current state of the
59 * cdev in use to determine the next_target.
60 */
61 cdev->ops->get_cur_state(cdev, &cur_state);
62 next_target = instance->target;
63
64 switch (trend) {
65 case THERMAL_TREND_RAISING:
66 if (throttle) {
67 next_target = cur_state < instance->upper ?
68 (cur_state + 1) : instance->upper;
69 if (next_target < instance->lower)
70 next_target = instance->lower;
71 }
72 break;
73 case THERMAL_TREND_RAISE_FULL:
74 if (throttle)
75 next_target = instance->upper;
76 break;
77 case THERMAL_TREND_DROPPING:
78 if (cur_state == instance->lower) {
79 if (!throttle)
80 next_target = THERMAL_NO_TARGET;
81 } else {
82 next_target = cur_state - 1;
83 if (next_target > instance->upper)
84 next_target = instance->upper;
85 }
86 break;
87 case THERMAL_TREND_DROP_FULL:
88 if (cur_state == instance->lower) {
89 if (!throttle)
90 next_target = THERMAL_NO_TARGET;
91 } else
92 next_target = instance->lower;
93 break;
94 default:
95 break;
96 }
97
98 return next_target;
99}
100
101static void update_passive_instance(struct thermal_zone_device *tz,
102 enum thermal_trip_type type, int value)
103{
104 /*
105 * If value is +1, activate a passive instance.
106 * If value is -1, deactivate a passive instance.
107 */
108 if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
109 tz->passive += value;
110}
111
112static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
113{
114 long trip_temp;
115 enum thermal_trip_type trip_type;
116 enum thermal_trend trend;
117 struct thermal_instance *instance;
118 bool throttle = false;
119 int old_target;
120
121 if (trip == THERMAL_TRIPS_NONE) {
122 trip_temp = tz->forced_passive;
123 trip_type = THERMAL_TRIPS_NONE;
124 } else {
125 tz->ops->get_trip_temp(tz, trip, &trip_temp);
126 tz->ops->get_trip_type(tz, trip, &trip_type);
127 }
128
129 trend = get_tz_trend(tz, trip);
130
131 if (tz->temperature >= trip_temp)
132 throttle = true;
133
134 mutex_lock(&tz->lock);
135
136 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
137 if (instance->trip != trip)
138 continue;
139
140 old_target = instance->target;
141 instance->target = get_target_state(instance, trend, throttle);
142
143 if (old_target == instance->target)
144 continue;
145
146 /* Activate a passive thermal instance */
147 if (old_target == THERMAL_NO_TARGET &&
148 instance->target != THERMAL_NO_TARGET)
149 update_passive_instance(tz, trip_type, 1);
150 /* Deactivate a passive thermal instance */
151 else if (old_target != THERMAL_NO_TARGET &&
152 instance->target == THERMAL_NO_TARGET)
153 update_passive_instance(tz, trip_type, -1);
154
155
156 instance->cdev->updated = false; /* cdev needs update */
157 }
158
159 mutex_unlock(&tz->lock);
160}
161
162/**
163 * step_wise_throttle - throttles devices asscciated with the given zone
164 * @tz - thermal_zone_device
165 * @trip - the trip point
166 * @trip_type - type of the trip point
167 *
168 * Throttling Logic: This uses the trend of the thermal zone to throttle.
169 * If the thermal zone is 'heating up' this throttles all the cooling
170 * devices associated with the zone and its particular trip point, by one
171 * step. If the zone is 'cooling down' it brings back the performance of
172 * the devices by one step.
173 */
174static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
175{
176 struct thermal_instance *instance;
177
178 thermal_zone_trip_update(tz, trip);
179
180 if (tz->forced_passive)
181 thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
182
183 mutex_lock(&tz->lock);
184
185 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
186 thermal_cdev_update(instance->cdev);
187
188 mutex_unlock(&tz->lock);
189
190 return 0;
191}
192
193static struct thermal_governor thermal_gov_step_wise = {
194 .name = "step_wise",
195 .throttle = step_wise_throttle,
196};
197
198int thermal_gov_step_wise_register(void)
199{
200 return thermal_register_governor(&thermal_gov_step_wise);
201}
202
203void thermal_gov_step_wise_unregister(void)
204{
205 thermal_unregister_governor(&thermal_gov_step_wise);
206}