116 lines
3.3 KiB
C
116 lines
3.3 KiB
C
// 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,
|
|
const struct thermal_trip *trip)
|
|
{
|
|
int trip_index = thermal_zone_trip_id(tz, trip);
|
|
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,
|
|
const struct thermal_trip *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);
|