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 
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 	struct thermal_trip trip;
25 	int count;
26 
27 	for (count = 0; count < tz->num_trips; count++) {
28 		__thermal_zone_get_trip(tz, count, &trip);
29 		if (tz->temperature < trip.temperature)
30 			break;
31 	}
32 
33 	/*
34 	 * count > 0 only if temperature is greater than first trip
35 	 * point, in which case, trip_point = count - 1
36 	 */
37 	if (count > 0)
38 		trace_thermal_zone_trip(tz, count - 1, trip.type);
39 
40 	return count;
41 }
42 
43 static 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 index
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  */
68 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
69 {
70 	struct thermal_instance *instance;
71 	int total_weight = 0;
72 	int total_instance = 0;
73 	int cur_trip_level = get_trip_level(tz);
74 
75 	lockdep_assert_held(&tz->lock);
76 
77 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
78 		if (instance->trip != trip)
79 			continue;
80 
81 		total_weight += instance->weight;
82 		total_instance++;
83 	}
84 
85 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
86 		int percentage;
87 		struct thermal_cooling_device *cdev = instance->cdev;
88 
89 		if (instance->trip != trip)
90 			continue;
91 
92 		if (!total_weight)
93 			percentage = 100 / total_instance;
94 		else
95 			percentage = (instance->weight * 100) / total_weight;
96 
97 		instance->target = get_target_state(tz, cdev, percentage,
98 						    cur_trip_level);
99 
100 		mutex_lock(&cdev->lock);
101 		__thermal_cdev_update(cdev);
102 		mutex_unlock(&cdev->lock);
103 	}
104 
105 	return 0;
106 }
107 
108 static struct thermal_governor thermal_gov_fair_share = {
109 	.name		= "fair_share",
110 	.throttle	= fair_share_throttle,
111 };
112 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);
113