/* * gov_bang_bang.c - A simple thermal throttling governor using hysteresis * * Copyright (C) 2014 Peter Feuerer * * Based on step_wise.c with following Copyrights: * Copyright (C) 2012 Intel Corp * Copyright (C) 2012 Durgadoss R * * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, version 2. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See * the GNU General Public License for more details. * */ #include #include "thermal_core.h" static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip) { long trip_temp; unsigned long trip_hyst; struct thermal_instance *instance; tz->ops->get_trip_temp(tz, trip, &trip_temp); tz->ops->get_trip_hyst(tz, trip, &trip_hyst); dev_dbg(&tz->device, "Trip%d[temp=%ld]:temp=%d:hyst=%ld\n", trip, trip_temp, tz->temperature, trip_hyst); mutex_lock(&tz->lock); list_for_each_entry(instance, &tz->thermal_instances, tz_node) { if (instance->trip != trip) continue; /* in case fan is in initial state, switch the fan off */ if (instance->target == THERMAL_NO_TARGET) instance->target = 0; /* in case fan is neither on nor off set the fan to active */ if (instance->target != 0 && instance->target != 1) { pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n", instance->name, instance->target); instance->target = 1; } /* * enable fan when temperature exceeds trip_temp and disable * the fan in case it falls below trip_temp minus hysteresis */ if (instance->target == 0 && tz->temperature >= trip_temp) instance->target = 1; else if (instance->target == 1 && tz->temperature < trip_temp - trip_hyst) instance->target = 0; dev_dbg(&instance->cdev->device, "target=%d\n", (int)instance->target); instance->cdev->updated = false; /* cdev needs update */ } mutex_unlock(&tz->lock); } /** * bang_bang_control - controls devices associated with the given zone * @tz - thermal_zone_device * @trip - the trip point * * Regulation Logic: a two point regulation, deliver cooling state depending * on the previous state shown in this diagram: * * Fan: OFF ON * * | * | * trip_temp: +---->+ * | | ^ * | | | * | | Temperature * (trip_temp - hyst): +<----+ * | * | * | * * * If the fan is not running and temperature exceeds trip_temp, the fan * gets turned on. * * In case the fan is running, temperature must fall below * (trip_temp - hyst) so that the fan gets turned off again. * */ static int bang_bang_control(struct thermal_zone_device *tz, int trip) { struct thermal_instance *instance; thermal_zone_trip_update(tz, trip); mutex_lock(&tz->lock); list_for_each_entry(instance, &tz->thermal_instances, tz_node) thermal_cdev_update(instance->cdev); mutex_unlock(&tz->lock); return 0; } static struct thermal_governor thermal_gov_bang_bang = { .name = "bang_bang", .throttle = bang_bang_control, }; int thermal_gov_bang_bang_register(void) { return thermal_register_governor(&thermal_gov_bang_bang); } void thermal_gov_bang_bang_unregister(void) { thermal_unregister_governor(&thermal_gov_bang_bang); }