linux/drivers/thermal/gov_bang_bang.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
 *
 *  Copyright (C) 2014 Peter Kaestle <[email protected]>
 *
 *  Based on step_wise.c with following Copyrights:
 *  Copyright (C) 2012 Intel Corp
 *  Copyright (C) 2012 Durgadoss R <[email protected]>
 */

#include <linux/thermal.h>

#include "thermal_core.h"

/**
 * 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)
{ … }

static struct thermal_governor thermal_gov_bang_bang = …;
THERMAL_GOVERNOR_DECLARE(…) …;