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// 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 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);
mutex_lock(&instance->cdev->lock);
__thermal_cdev_update(instance->cdev);
mutex_unlock(&instance->cdev->lock);
}
/**
* bang_bang_control - controls devices associated with the given zone
* @tz: thermal_zone_device
* @trip: the trip point
* @crossed_up: whether or not the trip has been crossed on the way up
*
* 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 void bang_bang_control(struct thermal_zone_device *tz,
const struct thermal_trip *trip,
bool crossed_up)
{
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, &tz->thermal_instances, tz_node) {
if (instance->trip == trip)
bang_bang_set_instance_target(instance, crossed_up);
}
}
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;
if (tz->temperature >= td->threshold ||
trip->temperature == THERMAL_TEMP_INVALID ||
trip->type == THERMAL_TRIP_CRITICAL ||
trip->type == THERMAL_TRIP_HOT)
continue;
/*
* If the initial cooling device state is "on", but the zone
* temperature is not above the trip point, the core will not
* call bang_bang_control() until the zone temperature reaches
* the trip point temperature which may be never. In those
* cases, set the initial state of the cooling device to 0.
*/
list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
if (!instance->initialized && instance->trip == trip)
bang_bang_set_instance_target(instance, 0);
}
}
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_control,
.manage = bang_bang_manage,
.update_tz = bang_bang_update_tz,
};
THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);
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