1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * gov_bang_bang.c - A simple thermal throttling governor using hysteresis 4 * 5 * Copyright (C) 2014 Peter Kaestle <peter@piie.net> 6 * 7 * Based on step_wise.c with following Copyrights: 8 * Copyright (C) 2012 Intel Corp 9 * Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com> 10 */ 11 12 #include <linux/thermal.h> 13 14 #include "thermal_core.h" 15 16 static void bang_bang_set_instance_target(struct thermal_instance *instance, 17 unsigned int target) 18 { 19 if (instance->target != 0 && instance->target != 1 && 20 instance->target != THERMAL_NO_TARGET) 21 pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n", 22 instance->target, instance->name); 23 24 /* 25 * Enable the fan when the trip is crossed on the way up and disable it 26 * when the trip is crossed on the way down. 27 */ 28 instance->target = target; 29 instance->initialized = true; 30 31 dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target); 32 33 mutex_lock(&instance->cdev->lock); 34 __thermal_cdev_update(instance->cdev); 35 mutex_unlock(&instance->cdev->lock); 36 } 37 38 /** 39 * bang_bang_control - controls devices associated with the given zone 40 * @tz: thermal_zone_device 41 * @trip: the trip point 42 * @crossed_up: whether or not the trip has been crossed on the way up 43 * 44 * Regulation Logic: a two point regulation, deliver cooling state depending 45 * on the previous state shown in this diagram: 46 * 47 * Fan: OFF ON 48 * 49 * | 50 * | 51 * trip_temp: +---->+ 52 * | | ^ 53 * | | | 54 * | | Temperature 55 * (trip_temp - hyst): +<----+ 56 * | 57 * | 58 * | 59 * 60 * * If the fan is not running and temperature exceeds trip_temp, the fan 61 * gets turned on. 62 * * In case the fan is running, temperature must fall below 63 * (trip_temp - hyst) so that the fan gets turned off again. 64 * 65 */ 66 static void bang_bang_control(struct thermal_zone_device *tz, 67 const struct thermal_trip *trip, 68 bool crossed_up) 69 { 70 struct thermal_instance *instance; 71 72 lockdep_assert_held(&tz->lock); 73 74 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", 75 thermal_zone_trip_id(tz, trip), trip->temperature, 76 tz->temperature, trip->hysteresis); 77 78 list_for_each_entry(instance, &tz->thermal_instances, tz_node) { 79 if (instance->trip == trip) 80 bang_bang_set_instance_target(instance, crossed_up); 81 } 82 } 83 84 static void bang_bang_manage(struct thermal_zone_device *tz) 85 { 86 const struct thermal_trip_desc *td; 87 struct thermal_instance *instance; 88 89 /* If the code below has run already, nothing needs to be done. */ 90 if (tz->governor_data) 91 return; 92 93 for_each_trip_desc(tz, td) { 94 const struct thermal_trip *trip = &td->trip; 95 96 if (tz->temperature >= td->threshold || 97 trip->temperature == THERMAL_TEMP_INVALID || 98 trip->type == THERMAL_TRIP_CRITICAL || 99 trip->type == THERMAL_TRIP_HOT) 100 continue; 101 102 /* 103 * If the initial cooling device state is "on", but the zone 104 * temperature is not above the trip point, the core will not 105 * call bang_bang_control() until the zone temperature reaches 106 * the trip point temperature which may be never. In those 107 * cases, set the initial state of the cooling device to 0. 108 */ 109 list_for_each_entry(instance, &tz->thermal_instances, tz_node) { 110 if (!instance->initialized && instance->trip == trip) 111 bang_bang_set_instance_target(instance, 0); 112 } 113 } 114 115 tz->governor_data = (void *)true; 116 } 117 118 static void bang_bang_update_tz(struct thermal_zone_device *tz, 119 enum thermal_notify_event reason) 120 { 121 /* 122 * Let bang_bang_manage() know that it needs to walk trips after binding 123 * a new cdev and after system resume. 124 */ 125 if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME) 126 tz->governor_data = NULL; 127 } 128 129 static struct thermal_governor thermal_gov_bang_bang = { 130 .name = "bang_bang", 131 .trip_crossed = bang_bang_control, 132 .manage = bang_bang_manage, 133 .update_tz = bang_bang_update_tz, 134 }; 135 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang); 136