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 <trace/events/thermal.h>
15 
16 #include "thermal_core.h"
17 
18 /**
19  * get_trip_level: - obtains the current trip level for a zone
20  * @tz:		thermal zone device
21  */
22 static int get_trip_level(struct thermal_zone_device *tz)
23 {
24 	int count = 0;
25 	int trip_temp;
26 	enum thermal_trip_type trip_type;
27 
28 	if (tz->num_trips == 0 || !tz->ops->get_trip_temp)
29 		return 0;
30 
31 	for (count = 0; count < tz->num_trips; count++) {
32 		tz->ops->get_trip_temp(tz, count, &trip_temp);
33 		if (tz->temperature < trip_temp)
34 			break;
35 	}
36 
37 	/*
38 	 * count > 0 only if temperature is greater than first trip
39 	 * point, in which case, trip_point = count - 1
40 	 */
41 	if (count > 0) {
42 		tz->ops->get_trip_type(tz, count - 1, &trip_type);
43 		trace_thermal_zone_trip(tz, count - 1, trip_type);
44 	}
45 
46 	return count;
47 }
48 
49 static long get_target_state(struct thermal_zone_device *tz,
50 		struct thermal_cooling_device *cdev, int percentage, int level)
51 {
52 	return (long)(percentage * level * cdev->max_state) / (100 * tz->num_trips);
53 }
54 
55 /**
56  * fair_share_throttle - throttles devices associated with the given zone
57  * @tz: thermal_zone_device
58  * @trip: trip point index
59  *
60  * Throttling Logic: This uses three parameters to calculate the new
61  * throttle state of the cooling devices associated with the given zone.
62  *
63  * Parameters used for Throttling:
64  * P1. max_state: Maximum throttle state exposed by the cooling device.
65  * P2. percentage[i]/100:
66  *	How 'effective' the 'i'th device is, in cooling the given zone.
67  * P3. cur_trip_level/max_no_of_trips:
68  *	This describes the extent to which the devices should be throttled.
69  *	We do not want to throttle too much when we trip a lower temperature,
70  *	whereas the throttling is at full swing if we trip critical levels.
71  *	(Heavily assumes the trip points are in ascending order)
72  * new_state of cooling device = P3 * P2 * P1
73  */
74 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
75 {
76 	struct thermal_instance *instance;
77 	int total_weight = 0;
78 	int total_instance = 0;
79 	int cur_trip_level = get_trip_level(tz);
80 
81 	lockdep_assert_held(&tz->lock);
82 
83 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
84 		if (instance->trip != trip)
85 			continue;
86 
87 		total_weight += instance->weight;
88 		total_instance++;
89 	}
90 
91 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
92 		int percentage;
93 		struct thermal_cooling_device *cdev = instance->cdev;
94 
95 		if (instance->trip != trip)
96 			continue;
97 
98 		if (!total_weight)
99 			percentage = 100 / total_instance;
100 		else
101 			percentage = (instance->weight * 100) / total_weight;
102 
103 		instance->target = get_target_state(tz, cdev, percentage,
104 						    cur_trip_level);
105 
106 		mutex_lock(&cdev->lock);
107 		__thermal_cdev_update(cdev);
108 		mutex_unlock(&cdev->lock);
109 	}
110 
111 	return 0;
112 }
113 
114 static struct thermal_governor thermal_gov_fair_share = {
115 	.name		= "fair_share",
116 	.throttle	= fair_share_throttle,
117 };
118 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);
119