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 thermal_cdev_update_nocheck(instance->cdev); 34 } 35 36 /** 37 * bang_bang_control - controls devices associated with the given zone 38 * @tz: thermal_zone_device 39 * @trip: the trip point 40 * @crossed_up: whether or not the trip has been crossed on the way up 41 * 42 * Regulation Logic: a two point regulation, deliver cooling state depending 43 * on the previous state shown in this diagram: 44 * 45 * Fan: OFF ON 46 * 47 * | 48 * | 49 * trip_temp: +---->+ 50 * | | ^ 51 * | | | 52 * | | Temperature 53 * (trip_temp - hyst): +<----+ 54 * | 55 * | 56 * | 57 * 58 * * If the fan is not running and temperature exceeds trip_temp, the fan 59 * gets turned on. 60 * * In case the fan is running, temperature must fall below 61 * (trip_temp - hyst) so that the fan gets turned off again. 62 * 63 */ 64 static void bang_bang_control(struct thermal_zone_device *tz, 65 const struct thermal_trip *trip, 66 bool crossed_up) 67 { 68 const struct thermal_trip_desc *td = trip_to_trip_desc(trip); 69 struct thermal_instance *instance; 70 71 lockdep_assert_held(&tz->lock); 72 73 dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", 74 thermal_zone_trip_id(tz, trip), trip->temperature, 75 tz->temperature, trip->hysteresis); 76 77 list_for_each_entry(instance, &td->thermal_instances, trip_node) 78 bang_bang_set_instance_target(instance, crossed_up); 79 } 80 81 static void bang_bang_manage(struct thermal_zone_device *tz) 82 { 83 const struct thermal_trip_desc *td; 84 struct thermal_instance *instance; 85 86 /* If the code below has run already, nothing needs to be done. */ 87 if (tz->governor_data) 88 return; 89 90 for_each_trip_desc(tz, td) { 91 const struct thermal_trip *trip = &td->trip; 92 bool turn_on; 93 94 if (trip->temperature == THERMAL_TEMP_INVALID || 95 trip->type == THERMAL_TRIP_CRITICAL || 96 trip->type == THERMAL_TRIP_HOT) 97 continue; 98 99 /* 100 * Adjust the target states for uninitialized thermal instances 101 * to the thermal zone temperature and the trip point threshold. 102 */ 103 turn_on = tz->temperature >= td->threshold; 104 list_for_each_entry(instance, &td->thermal_instances, trip_node) { 105 if (!instance->initialized) 106 bang_bang_set_instance_target(instance, turn_on); 107 } 108 } 109 110 tz->governor_data = (void *)true; 111 } 112 113 static void bang_bang_update_tz(struct thermal_zone_device *tz, 114 enum thermal_notify_event reason) 115 { 116 /* 117 * Let bang_bang_manage() know that it needs to walk trips after binding 118 * a new cdev and after system resume. 119 */ 120 if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME) 121 tz->governor_data = NULL; 122 } 123 124 static struct thermal_governor thermal_gov_bang_bang = { 125 .name = "bang_bang", 126 .trip_crossed = bang_bang_control, 127 .manage = bang_bang_manage, 128 .update_tz = bang_bang_update_tz, 129 }; 130 THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang); 131