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#include <linux/thermal.h>
 26#include <trace/events/thermal.h>
 27
 28#include "thermal_core.h"
 29
 30/**
 31 * get_trip_level: - obtains the current trip level for a zone
 32 * @tz:		thermal zone device
 33 */
 34static int get_trip_level(struct thermal_zone_device *tz)
 35{
 36	int count = 0;
 37	int trip_temp;
 38	enum thermal_trip_type trip_type;
 39
 40	if (tz->trips == 0 || !tz->ops->get_trip_temp)
 41		return 0;
 42
 43	for (count = 0; count < tz->trips; count++) {
 44		tz->ops->get_trip_temp(tz, count, &trip_temp);
 45		if (tz->temperature < trip_temp)
 46			break;
 47	}
 48
 49	/*
 50	 * count > 0 only if temperature is greater than first trip
 51	 * point, in which case, trip_point = count - 1
 52	 */
 53	if (count > 0) {
 54		tz->ops->get_trip_type(tz, count - 1, &trip_type);
 55		trace_thermal_zone_trip(tz, count - 1, trip_type);
 56	}
 57
 58	return count;
 59}
 60
 61static long get_target_state(struct thermal_zone_device *tz,
 62		struct thermal_cooling_device *cdev, int percentage, int level)
 63{
 64	unsigned long max_state;
 65
 66	cdev->ops->get_max_state(cdev, &max_state);
 67
 68	return (long)(percentage * level * max_state) / (100 * tz->trips);
 69}
 70
 71/**
 72 * fair_share_throttle - throttles devices associated with the given zone
 73 * @tz - thermal_zone_device
 74 *
 75 * Throttling Logic: This uses three parameters to calculate the new
 76 * throttle state of the cooling devices associated with the given zone.
 77 *
 78 * Parameters used for Throttling:
 79 * P1. max_state: Maximum throttle state exposed by the cooling device.
 80 * P2. percentage[i]/100:
 81 *	How 'effective' the 'i'th device is, in cooling the given zone.
 82 * P3. cur_trip_level/max_no_of_trips:
 83 *	This describes the extent to which the devices should be throttled.
 84 *	We do not want to throttle too much when we trip a lower temperature,
 85 *	whereas the throttling is at full swing if we trip critical levels.
 86 *	(Heavily assumes the trip points are in ascending order)
 87 * new_state of cooling device = P3 * P2 * P1
 88 */
 89static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
 90{
 91	struct thermal_instance *instance;
 92	int total_weight = 0;
 93	int total_instance = 0;
 94	int cur_trip_level = get_trip_level(tz);
 95
 96	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 97		if (instance->trip != trip)
 98			continue;
 99
100		total_weight += instance->weight;
101		total_instance++;
102	}
103
104	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
105		int percentage;
106		struct thermal_cooling_device *cdev = instance->cdev;
107
108		if (instance->trip != trip)
109			continue;
110
111		if (!total_weight)
112			percentage = 100 / total_instance;
113		else
114			percentage = (instance->weight * 100) / total_weight;
115
116		instance->target = get_target_state(tz, cdev, percentage,
117						    cur_trip_level);
118
119		instance->cdev->updated = false;
120		thermal_cdev_update(cdev);
121	}
122	return 0;
123}
124
125static struct thermal_governor thermal_gov_fair_share = {
126	.name		= "fair_share",
127	.throttle	= fair_share_throttle,
128};
129
130int thermal_gov_fair_share_register(void)
131{
132	return thermal_register_governor(&thermal_gov_fair_share);
133}
134
135void thermal_gov_fair_share_unregister(void)
136{
137	thermal_unregister_governor(&thermal_gov_fair_share);
138}
139