1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fair_share.c - A simple weight based Thermal governor
4 *
5 * Copyright (C) 2012 Intel Corp
6 * Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
7 *
8 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 *
10 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
11 */
12
13#include <linux/thermal.h>
14#include "thermal_trace.h"
15
16#include "thermal_core.h"
17
18static int get_trip_level(struct thermal_zone_device *tz)
19{
20 const struct thermal_trip *trip, *level_trip = NULL;
21 int trip_level = -1;
22
23 for_each_trip(tz, trip) {
24 if (trip->temperature >= tz->temperature)
25 continue;
26
27 trip_level++;
28
29 if (!level_trip || trip->temperature > level_trip->temperature)
30 level_trip = trip;
31 }
32
33 /* Bail out if the temperature is not greater than any trips. */
34 if (trip_level < 0)
35 return 0;
36
37 trace_thermal_zone_trip(tz, trip: thermal_zone_trip_id(tz, trip: level_trip),
38 trip_type: level_trip->type);
39
40 return trip_level;
41}
42
43static long get_target_state(struct thermal_zone_device *tz,
44 struct thermal_cooling_device *cdev, int percentage, int level)
45{
46 return (long)(percentage * level * cdev->max_state) / (100 * tz->num_trips);
47}
48
49/**
50 * fair_share_throttle - throttles devices associated with the given zone
51 * @tz: thermal_zone_device
52 * @trip: trip point
53 *
54 * Throttling Logic: This uses three parameters to calculate the new
55 * throttle state of the cooling devices associated with the given zone.
56 *
57 * Parameters used for Throttling:
58 * P1. max_state: Maximum throttle state exposed by the cooling device.
59 * P2. percentage[i]/100:
60 * How 'effective' the 'i'th device is, in cooling the given zone.
61 * P3. cur_trip_level/max_no_of_trips:
62 * This describes the extent to which the devices should be throttled.
63 * We do not want to throttle too much when we trip a lower temperature,
64 * whereas the throttling is at full swing if we trip critical levels.
65 * (Heavily assumes the trip points are in ascending order)
66 * new_state of cooling device = P3 * P2 * P1
67 */
68static int fair_share_throttle(struct thermal_zone_device *tz,
69 const struct thermal_trip *trip)
70{
71 struct thermal_instance *instance;
72 int total_weight = 0;
73 int total_instance = 0;
74 int cur_trip_level = get_trip_level(tz);
75
76 lockdep_assert_held(&tz->lock);
77
78 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
79 if (instance->trip != trip)
80 continue;
81
82 total_weight += instance->weight;
83 total_instance++;
84 }
85
86 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
87 int percentage;
88 struct thermal_cooling_device *cdev = instance->cdev;
89
90 if (instance->trip != trip)
91 continue;
92
93 if (!total_weight)
94 percentage = 100 / total_instance;
95 else
96 percentage = (instance->weight * 100) / total_weight;
97
98 instance->target = get_target_state(tz, cdev, percentage,
99 level: cur_trip_level);
100
101 mutex_lock(&cdev->lock);
102 __thermal_cdev_update(cdev);
103 mutex_unlock(lock: &cdev->lock);
104 }
105
106 return 0;
107}
108
109static struct thermal_governor thermal_gov_fair_share = {
110 .name = "fair_share",
111 .throttle = fair_share_throttle,
112};
113THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);
114

source code of linux/drivers/thermal/gov_fair_share.c