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 */
get_target_state(struct thermal_instance * instance,enum thermal_trend trend,bool throttle)49 static 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
55 cdev->ops->get_cur_state(cdev, &cur_state);
56
57 switch (trend) {
58 case THERMAL_TREND_RAISING:
59 if (throttle) {
60 cur_state = cur_state < instance->upper ?
61 (cur_state + 1) : instance->upper;
62 if (cur_state < instance->lower)
63 cur_state = instance->lower;
64 }
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 if (cur_state > instance->upper)
77 cur_state = instance->upper;
78 }
79 break;
80 case THERMAL_TREND_DROP_FULL:
81 if (cur_state == instance->lower) {
82 if (!throttle)
83 cur_state = -1;
84 } else
85 cur_state = instance->lower;
86 break;
87 default:
88 break;
89 }
90
91 return cur_state;
92 }
93
update_passive_instance(struct thermal_zone_device * tz,enum thermal_trip_type type,int value)94 static void update_passive_instance(struct thermal_zone_device *tz,
95 enum thermal_trip_type type, int value)
96 {
97 /*
98 * If value is +1, activate a passive instance.
99 * If value is -1, deactivate a passive instance.
100 */
101 if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
102 tz->passive += value;
103 }
104
thermal_zone_trip_update(struct thermal_zone_device * tz,int trip)105 static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
106 {
107 long trip_temp;
108 enum thermal_trip_type trip_type;
109 enum thermal_trend trend;
110 struct thermal_instance *instance;
111 bool throttle = false;
112 int old_target;
113
114 if (trip == THERMAL_TRIPS_NONE) {
115 trip_temp = tz->forced_passive;
116 trip_type = THERMAL_TRIPS_NONE;
117 } else {
118 tz->ops->get_trip_temp(tz, trip, &trip_temp);
119 tz->ops->get_trip_type(tz, trip, &trip_type);
120 }
121
122 trend = get_tz_trend(tz, trip);
123
124 if (tz->temperature >= trip_temp)
125 throttle = true;
126
127 mutex_lock(&tz->lock);
128
129 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
130 if (instance->trip != trip)
131 continue;
132
133 old_target = instance->target;
134 instance->target = get_target_state(instance, trend, throttle);
135
136 /* Activate a passive thermal instance */
137 if (old_target == THERMAL_NO_TARGET &&
138 instance->target != THERMAL_NO_TARGET)
139 update_passive_instance(tz, trip_type, 1);
140 /* Deactivate a passive thermal instance */
141 else if (old_target != THERMAL_NO_TARGET &&
142 instance->target == THERMAL_NO_TARGET)
143 update_passive_instance(tz, trip_type, -1);
144
145
146 instance->cdev->updated = false; /* cdev needs update */
147 }
148
149 mutex_unlock(&tz->lock);
150 }
151
152 /**
153 * step_wise_throttle - throttles devices asscciated with the given zone
154 * @tz - thermal_zone_device
155 * @trip - the trip point
156 * @trip_type - type of the trip point
157 *
158 * Throttling Logic: This uses the trend of the thermal zone to throttle.
159 * If the thermal zone is 'heating up' this throttles all the cooling
160 * devices associated with the zone and its particular trip point, by one
161 * step. If the zone is 'cooling down' it brings back the performance of
162 * the devices by one step.
163 */
step_wise_throttle(struct thermal_zone_device * tz,int trip)164 static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
165 {
166 struct thermal_instance *instance;
167
168 thermal_zone_trip_update(tz, trip);
169
170 if (tz->forced_passive)
171 thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
172
173 mutex_lock(&tz->lock);
174
175 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
176 thermal_cdev_update(instance->cdev);
177
178 mutex_unlock(&tz->lock);
179
180 return 0;
181 }
182
183 static struct thermal_governor thermal_gov_step_wise = {
184 .name = "step_wise",
185 .throttle = step_wise_throttle,
186 };
187
thermal_gov_step_wise_register(void)188 int thermal_gov_step_wise_register(void)
189 {
190 return thermal_register_governor(&thermal_gov_step_wise);
191 }
192
thermal_gov_step_wise_unregister(void)193 void thermal_gov_step_wise_unregister(void)
194 {
195 thermal_unregister_governor(&thermal_gov_step_wise);
196 }
197