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 * Regulation Logic: a two point regulation, deliver cooling state depending 12 * on the previous state shown in this diagram: 13 * 14 * Fan: OFF ON 15 * 16 * | 17 * | 18 * trip_temp: +---->+ 19 * | | ^ 20 * | | | 21 * | | Temperature 22 * (trip_temp - hyst): +<----+ 23 * | 24 * | 25 * | 26 * 27 * * If the fan is not running and temperature exceeds trip_temp, the fan 28 * gets turned on. 29 * * In case the fan is running, temperature must fall below 30 * (trip_temp - hyst) so that the fan gets turned off again. 31 */ 32 33 #include <linux/thermal.h> 34 35 #include "thermal_core.h" 36 37 static void bang_bang_set_instance_target(struct thermal_instance *instance, 38 unsigned int target) 39 { 40 if (instance->target != 0 && instance->target != 1 && 41 instance->target != THERMAL_NO_TARGET) 42 pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n", 43 instance->target, instance->name); 44 45 /* 46 * Enable the fan when the trip is crossed on the way up and disable it 47 * when the trip is crossed on the way down. 48 */ 49 instance->target = target; 50 instance->initialized = true; 51 52 dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target); 53 54 thermal_cdev_update_nocheck(instance->cdev); 55 } 56 57 /** 58 * bang_bang_trip_crossed - controls devices associated with the given zone 59 * @tz: thermal_zone_device 60 * @trip: the trip point 61 * @upward: whether or not the trip has been crossed on the way up 62 */ 63 static void bang_bang_trip_crossed(struct thermal_zone_device *tz, 64 const struct thermal_trip *trip, 65 bool upward) 66 { 67 const struct thermal_trip_desc *td = trip_to_trip_desc(trip); 68 struct thermal_instance *instance; 69 70 lockdep_assert_held(&tz->lock); 71 72 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", 73 thermal_zone_trip_id(tz, trip), trip->temperature, 74 tz->temperature, trip->hysteresis); 75 76 list_for_each_entry(instance, &td->thermal_instances, trip_node) 77 bang_bang_set_instance_target(instance, upward); 78 } 79 80 static void bang_bang_manage(struct thermal_zone_device *tz) 81 { 82 const struct thermal_trip_desc *td; 83 struct thermal_instance *instance; 84 85 /* If the code below has run already, nothing needs to be done. */ 86 if (tz->governor_data) 87 return; 88 89 for_each_trip_desc(tz, td) { 90 const struct thermal_trip *trip = &td->trip; 91 bool turn_on; 92 93 if (trip->temperature == THERMAL_TEMP_INVALID || 94 trip->type == THERMAL_TRIP_CRITICAL || 95 trip->type == THERMAL_TRIP_HOT) 96 continue; 97 98 /* 99 * Adjust the target states for uninitialized thermal instances 100 * to the thermal zone temperature and the trip point threshold. 101 */ 102 turn_on = tz->temperature >= td->threshold; 103 list_for_each_entry(instance, &td->thermal_instances, trip_node) { 104 if (!instance->initialized) 105 bang_bang_set_instance_target(instance, turn_on); 106 } 107 } 108 109 tz->governor_data = (void *)true; 110 } 111 112 static void bang_bang_update_tz(struct thermal_zone_device *tz, 113 enum thermal_notify_event reason) 114 { 115 /* 116 * Let bang_bang_manage() know that it needs to walk trips after binding 117 * a new cdev and after system resume. 118 */ 119 if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME) 120 tz->governor_data = NULL; 121 } 122 123 static struct thermal_governor thermal_gov_bang_bang = { 124 .name = "bang_bang", 125 .trip_crossed = bang_bang_trip_crossed, 126 .manage = bang_bang_manage, 127 .update_tz = bang_bang_update_tz, 128 }; 129 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang); 130