diff options
Diffstat (limited to 'drivers/thermal/gov_bang_bang.c')
| -rw-r--r-- | drivers/thermal/gov_bang_bang.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/drivers/thermal/gov_bang_bang.c b/drivers/thermal/gov_bang_bang.c new file mode 100644 index 000000000000..c5dd76b2ee74 --- /dev/null +++ b/drivers/thermal/gov_bang_bang.c @@ -0,0 +1,131 @@ +/* + * gov_bang_bang.c - A simple thermal throttling governor using hysteresis + * + * Copyright (C) 2014 Peter Feuerer <peter@piie.net> + * + * Based on step_wise.c with following Copyrights: + * Copyright (C) 2012 Intel Corp + * Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com> + * + * + * 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 <linux/thermal.h> + +#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); +} |