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_desc *level_td = NULL;
 21	const struct thermal_trip_desc *td;
 22	int trip_level = -1;
 23
 24	for_each_trip_desc(tz, td) {
 25		if (td->threshold > tz->temperature)
 26			continue;
 27
 28		trip_level++;
 29
 30		if (!level_td || td->threshold > level_td->threshold)
 31			level_td = td;
 32	}
 33
 34	/*  Bail out if the temperature is not greater than any trips. */
 35	if (trip_level < 0)
 36		return 0;
 37
 38	trace_thermal_zone_trip(tz, thermal_zone_trip_id(tz, &level_td->trip),
 39				level_td->trip.type);
 40
 41	return trip_level;
 42}
 43
 44/**
 45 * fair_share_throttle - throttles devices associated with the given zone
 46 * @tz: thermal_zone_device
 47 * @td: trip point descriptor
 48 * @trip_level: number of trips crossed by the zone temperature
 49 *
 50 * Throttling Logic: This uses three parameters to calculate the new
 51 * throttle state of the cooling devices associated with the given zone.
 52 *
 53 * Parameters used for Throttling:
 54 * P1. max_state: Maximum throttle state exposed by the cooling device.
 55 * P2. weight[i]/total_weight:
 56 *	How 'effective' the 'i'th device is, in cooling the given zone.
 57 * P3. trip_level/max_no_of_trips:
 58 *	This describes the extent to which the devices should be throttled.
 59 *	We do not want to throttle too much when we trip a lower temperature,
 60 *	whereas the throttling is at full swing if we trip critical levels.
 61 * new_state of cooling device = P3 * P2 * P1
 62 */
 63static void fair_share_throttle(struct thermal_zone_device *tz,
 64				const struct thermal_trip_desc *td,
 65				int trip_level)
 66{
 67	struct thermal_instance *instance;
 68	int total_weight = 0;
 69	int nr_instances = 0;
 70
 71	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
 72		total_weight += instance->weight;
 73		nr_instances++;
 74	}
 75
 76	list_for_each_entry(instance, &td->thermal_instances, trip_node) {
 77		struct thermal_cooling_device *cdev = instance->cdev;
 78		u64 dividend;
 79		u32 divisor;
 80
 81		dividend = trip_level;
 82		dividend *= cdev->max_state;
 83		divisor = tz->num_trips;
 84		if (total_weight) {
 85			dividend *= instance->weight;
 86			divisor *= total_weight;
 87		} else {
 88			divisor *= nr_instances;
 89		}
 90		instance->target = div_u64(dividend, divisor);
 91
 92		thermal_cdev_update_nocheck(cdev);
 93	}
 94}
 95
 96static void fair_share_manage(struct thermal_zone_device *tz)
 97{
 98	int trip_level = get_trip_level(tz);
 99	const struct thermal_trip_desc *td;
100
101	lockdep_assert_held(&tz->lock);
102
103	for_each_trip_desc(tz, td) {
104		const struct thermal_trip *trip = &td->trip;
105
106		if (trip->temperature == THERMAL_TEMP_INVALID ||
107		    trip->type == THERMAL_TRIP_CRITICAL ||
108		    trip->type == THERMAL_TRIP_HOT)
109			continue;
110
111		fair_share_throttle(tz, td, trip_level);
112	}
113}
114
115static struct thermal_governor thermal_gov_fair_share = {
116	.name	= "fair_share",
117	.manage	= fair_share_manage,
118};
119THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);