// 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 thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
  {

  	int trip_temp, trip_hyst;

  	struct thermal_instance *instance;
  
  	tz->ops->get_trip_temp(tz, trip, &trip_temp);

  
  	if (!tz->ops->get_trip_hyst) {
  		pr_warn_once("Undefined get_trip_hyst for thermal zone %s - "
  				"running with default hysteresis zero
  ", tz->type);
  		trip_hyst = 0;
  	} else
  		tz->ops->get_trip_hyst(tz, trip, &trip_hyst);

  	dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d
  ",

  				trip, trip_temp, tz->temperature,
  				trip_hyst);
  
  	mutex_lock(&tz->lock);
  
  	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
  ",
  					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_temp)
  			instance->target = 1;
  		else if (instance->target == 1 &&

  				tz->temperature <= trip_temp - trip_hyst)

  			instance->target = 0;
  
  		dev_dbg(&instance->cdev->device, "target=%d
  ",
  					(int)instance->target);

  		mutex_lock(&instance->cdev->lock);

  		instance->cdev->updated = false; /* cdev needs update */

  		mutex_unlock(&instance->cdev->lock);

  	}
  
  	mutex_unlock(&tz->lock);
  }
  
  /**
   * 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;
  
  	thermal_zone_trip_update(tz, trip);
  
  	mutex_lock(&tz->lock);
  
  	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
  		thermal_cdev_update(instance->cdev);
  
  	mutex_unlock(&tz->lock);
  
  	return 0;
  }
  
  static struct thermal_governor thermal_gov_bang_bang = {
  	.name		= "bang_bang",
  	.throttle	= bang_bang_control,
  };

  THERMAL_GOVERNOR_DECLARE(thermal_gov_bang_bang);