Root/drivers/thermal/fair_share.c

1/*
2 * fair_share.c - A simple weight based Thermal 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 * get_trip_level: - obtains the current trip level for a zone
34 * @tz: thermal zone device
35 */
36static int get_trip_level(struct thermal_zone_device *tz)
37{
38    int count = 0;
39    unsigned long trip_temp;
40
41    if (tz->trips == 0 || !tz->ops->get_trip_temp)
42        return 0;
43
44    for (count = 0; count < tz->trips; count++) {
45        tz->ops->get_trip_temp(tz, count, &trip_temp);
46        if (tz->temperature < trip_temp)
47            break;
48    }
49    return count;
50}
51
52static long get_target_state(struct thermal_zone_device *tz,
53        struct thermal_cooling_device *cdev, int weight, int level)
54{
55    unsigned long max_state;
56
57    cdev->ops->get_max_state(cdev, &max_state);
58
59    return (long)(weight * level * max_state) / (100 * tz->trips);
60}
61
62/**
63 * fair_share_throttle - throttles devices asscciated with the given zone
64 * @tz - thermal_zone_device
65 *
66 * Throttling Logic: This uses three parameters to calculate the new
67 * throttle state of the cooling devices associated with the given zone.
68 *
69 * Parameters used for Throttling:
70 * P1. max_state: Maximum throttle state exposed by the cooling device.
71 * P2. weight[i]/100:
72 * How 'effective' the 'i'th device is, in cooling the given zone.
73 * P3. cur_trip_level/max_no_of_trips:
74 * This describes the extent to which the devices should be throttled.
75 * We do not want to throttle too much when we trip a lower temperature,
76 * whereas the throttling is at full swing if we trip critical levels.
77 * (Heavily assumes the trip points are in ascending order)
78 * new_state of cooling device = P3 * P2 * P1
79 */
80static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
81{
82    const struct thermal_zone_params *tzp;
83    struct thermal_cooling_device *cdev;
84    struct thermal_instance *instance;
85    int i;
86    int cur_trip_level = get_trip_level(tz);
87
88    if (!tz->tzp || !tz->tzp->tbp)
89        return -EINVAL;
90
91    tzp = tz->tzp;
92
93    for (i = 0; i < tzp->num_tbps; i++) {
94        if (!tzp->tbp[i].cdev)
95            continue;
96
97        cdev = tzp->tbp[i].cdev;
98        instance = get_thermal_instance(tz, cdev, trip);
99        if (!instance)
100            continue;
101
102        instance->target = get_target_state(tz, cdev,
103                    tzp->tbp[i].weight, cur_trip_level);
104
105        instance->cdev->updated = false;
106        thermal_cdev_update(cdev);
107    }
108    return 0;
109}
110
111static struct thermal_governor thermal_gov_fair_share = {
112    .name = "fair_share",
113    .throttle = fair_share_throttle,
114    .owner = THIS_MODULE,
115};
116
117static int __init thermal_gov_fair_share_init(void)
118{
119    return thermal_register_governor(&thermal_gov_fair_share);
120}
121
122static void __exit thermal_gov_fair_share_exit(void)
123{
124    thermal_unregister_governor(&thermal_gov_fair_share);
125}
126
127/* This should load after thermal framework */
128fs_initcall(thermal_gov_fair_share_init);
129module_exit(thermal_gov_fair_share_exit);
130
131MODULE_AUTHOR("Durgadoss R");
132MODULE_DESCRIPTION("A simple weight based thermal throttling governor");
133MODULE_LICENSE("GPL");
134

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