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->trips == 0 || !tz->ops->get_trip_temp)
29 		return 0;
30 
31 	for (count = 0; count < tz->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 	unsigned long max_state;
53 
54 	cdev->ops->get_max_state(cdev, &max_state);
55 
56 	return (long)(percentage * level * max_state) / (100 * tz->trips);
57 }
58 
59 /**
60  * fair_share_throttle - throttles devices associated with the given zone
61  * @tz: thermal_zone_device
62  * @trip: trip point index
63  *
64  * Throttling Logic: This uses three parameters to calculate the new
65  * throttle state of the cooling devices associated with the given zone.
66  *
67  * Parameters used for Throttling:
68  * P1. max_state: Maximum throttle state exposed by the cooling device.
69  * P2. percentage[i]/100:
70  *	How 'effective' the 'i'th device is, in cooling the given zone.
71  * P3. cur_trip_level/max_no_of_trips:
72  *	This describes the extent to which the devices should be throttled.
73  *	We do not want to throttle too much when we trip a lower temperature,
74  *	whereas the throttling is at full swing if we trip critical levels.
75  *	(Heavily assumes the trip points are in ascending order)
76  * new_state of cooling device = P3 * P2 * P1
77  */
78 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
79 {
80 	struct thermal_instance *instance;
81 	int total_weight = 0;
82 	int total_instance = 0;
83 	int cur_trip_level = get_trip_level(tz);
84 
85 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
86 		if (instance->trip != trip)
87 			continue;
88 
89 		total_weight += instance->weight;
90 		total_instance++;
91 	}
92 
93 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
94 		int percentage;
95 		struct thermal_cooling_device *cdev = instance->cdev;
96 
97 		if (instance->trip != trip)
98 			continue;
99 
100 		if (!total_weight)
101 			percentage = 100 / total_instance;
102 		else
103 			percentage = (instance->weight * 100) / total_weight;
104 
105 		instance->target = get_target_state(tz, cdev, percentage,
106 						    cur_trip_level);
107 
108 		mutex_lock(&instance->cdev->lock);
109 		instance->cdev->updated = false;
110 		mutex_unlock(&instance->cdev->lock);
111 		thermal_cdev_update(cdev);
112 	}
113 	return 0;
114 }
115 
116 static struct thermal_governor thermal_gov_fair_share = {
117 	.name		= "fair_share",
118 	.throttle	= fair_share_throttle,
119 };
120 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);
121