diff options
Diffstat (limited to 'drivers/thermal/gov_bang_bang.c')
| -rw-r--r-- | drivers/thermal/gov_bang_bang.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/drivers/thermal/gov_bang_bang.c b/drivers/thermal/gov_bang_bang.c new file mode 100644 index 0000000000..49cdfaa3a9 --- /dev/null +++ b/drivers/thermal/gov_bang_bang.c @@ -0,0 +1,113 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * gov_bang_bang.c - A simple thermal throttling governor using hysteresis + * + * Copyright (C) 2014 Peter Kaestle <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> + */ + +#include <linux/thermal.h> + +#include "thermal_core.h" + +static int thermal_zone_trip_update(struct thermal_zone_device *tz, int trip_index) +{ + const struct thermal_trip *trip = &tz->trips[trip_index]; + struct thermal_instance *instance; + + if (!trip->hysteresis) + dev_info_once(&tz->device, + "Zero hysteresis value for thermal zone %s\n", tz->type); + + dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", + trip_index, trip->temperature, tz->temperature, + trip->hysteresis); + + 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->temperature) + instance->target = 1; + else if (instance->target == 1 && + tz->temperature <= trip->temperature - trip->hysteresis) + instance->target = 0; + + dev_dbg(&instance->cdev->device, "target=%d\n", + (int)instance->target); + + mutex_lock(&instance->cdev->lock); + instance->cdev->updated = false; /* cdev needs update */ + mutex_unlock(&instance->cdev->lock); + } + + return 0; +} + +/** + * 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; + int ret; + + lockdep_assert_held(&tz->lock); + + ret = thermal_zone_trip_update(tz, trip); + if (ret) + return ret; + + list_for_each_entry(instance, &tz->thermal_instances, tz_node) + thermal_cdev_update(instance->cdev); + + return 0; +} + +static struct thermal_governor thermal_gov_bang_bang = { + .name = "bang_bang", + .throttle = bang_bang_control, +}; +THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang); |