diff options
Diffstat (limited to 'drivers/thermal/gov_bang_bang.c')
| -rw-r--r-- | drivers/thermal/gov_bang_bang.c | 129 |
1 files changed, 129 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..51951967d67f --- /dev/null +++ b/drivers/thermal/gov_bang_bang.c @@ -0,0 +1,129 @@ +// 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> + * + * 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. + */ + +#include <linux/thermal.h> + +#include "thermal_core.h" + +static void bang_bang_set_instance_target(struct thermal_instance *instance, + unsigned int target) +{ + if (instance->target != 0 && instance->target != 1 && + instance->target != THERMAL_NO_TARGET) + pr_debug("Unexpected state %ld of thermal instance %s in bang-bang\n", + instance->target, instance->name); + + /* + * Enable the fan when the trip is crossed on the way up and disable it + * when the trip is crossed on the way down. + */ + instance->target = target; + instance->initialized = true; + + dev_dbg(&instance->cdev->device, "target=%ld\n", instance->target); + + thermal_cdev_update_nocheck(instance->cdev); +} + +/** + * bang_bang_trip_crossed - controls devices associated with the given zone + * @tz: thermal_zone_device + * @trip: the trip point + * @upward: whether or not the trip has been crossed on the way up + */ +static void bang_bang_trip_crossed(struct thermal_zone_device *tz, + const struct thermal_trip *trip, + bool upward) +{ + const struct thermal_trip_desc *td = trip_to_trip_desc(trip); + struct thermal_instance *instance; + + lockdep_assert_held(&tz->lock); + + dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", + thermal_zone_trip_id(tz, trip), trip->temperature, + tz->temperature, trip->hysteresis); + + list_for_each_entry(instance, &td->thermal_instances, trip_node) + bang_bang_set_instance_target(instance, upward); +} + +static void bang_bang_manage(struct thermal_zone_device *tz) +{ + const struct thermal_trip_desc *td; + struct thermal_instance *instance; + + /* If the code below has run already, nothing needs to be done. */ + if (tz->governor_data) + return; + + for_each_trip_desc(tz, td) { + const struct thermal_trip *trip = &td->trip; + bool turn_on; + + if (trip->temperature == THERMAL_TEMP_INVALID || + trip->type == THERMAL_TRIP_CRITICAL || + trip->type == THERMAL_TRIP_HOT) + continue; + + /* + * Adjust the target states for uninitialized thermal instances + * to the thermal zone temperature and the trip point threshold. + */ + turn_on = tz->temperature >= td->threshold; + list_for_each_entry(instance, &td->thermal_instances, trip_node) { + if (!instance->initialized) + bang_bang_set_instance_target(instance, turn_on); + } + } + + tz->governor_data = (void *)true; +} + +static void bang_bang_update_tz(struct thermal_zone_device *tz, + enum thermal_notify_event reason) +{ + /* + * Let bang_bang_manage() know that it needs to walk trips after binding + * a new cdev and after system resume. + */ + if (reason == THERMAL_TZ_BIND_CDEV || reason == THERMAL_TZ_RESUME) + tz->governor_data = NULL; +} + +static struct thermal_governor thermal_gov_bang_bang = { + .name = "bang_bang", + .trip_crossed = bang_bang_trip_crossed, + .manage = bang_bang_manage, + .update_tz = bang_bang_update_tz, +}; +THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang); |