// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  linux/drivers/devfreq/governor_simpleondemand.c
   *
   *  Copyright (C) 2011 Samsung Electronics
   *	MyungJoo Ham <myungjoo.ham@samsung.com>

   */
  
  #include <linux/errno.h>

  #include <linux/module.h>

  #include <linux/devfreq.h>
  #include <linux/math64.h>

  #include "governor.h"

  
  /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
  #define DFSO_UPTHRESHOLD	(90)
  #define DFSO_DOWNDIFFERENCTIAL	(5)
  static int devfreq_simple_ondemand_func(struct devfreq *df,
  					unsigned long *freq)
  {

  	int err;
  	struct devfreq_dev_status *stat;

  	unsigned long long a, b;
  	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
  	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
  	struct devfreq_simple_ondemand_data *data = df->data;

  	err = devfreq_update_stats(df);

  	if (err)
  		return err;

  	stat = &df->last_status;

  	if (data) {
  		if (data->upthreshold)
  			dfso_upthreshold = data->upthreshold;
  		if (data->downdifferential)
  			dfso_downdifferential = data->downdifferential;
  	}
  	if (dfso_upthreshold > 100 ||
  	    dfso_upthreshold < dfso_downdifferential)
  		return -EINVAL;
  
  	/* Assume MAX if it is going to be divided by zero */

  	if (stat->total_time == 0) {

  		*freq = DEVFREQ_MAX_FREQ;

  		return 0;
  	}
  
  	/* Prevent overflow */

  	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
  		stat->busy_time >>= 7;
  		stat->total_time >>= 7;

  	}
  
  	/* Set MAX if it's busy enough */

  	if (stat->busy_time * 100 >
  	    stat->total_time * dfso_upthreshold) {

  		*freq = DEVFREQ_MAX_FREQ;

  		return 0;
  	}
  
  	/* Set MAX if we do not know the initial frequency */

  	if (stat->current_frequency == 0) {

  		*freq = DEVFREQ_MAX_FREQ;

  		return 0;
  	}
  
  	/* Keep the current frequency */

  	if (stat->busy_time * 100 >
  	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
  		*freq = stat->current_frequency;

  		return 0;
  	}
  
  	/* Set the desired frequency based on the load */

  	a = stat->busy_time;
  	a *= stat->current_frequency;
  	b = div_u64(a, stat->total_time);

  	b *= 100;
  	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
  	*freq = (unsigned long) b;
  
  	return 0;
  }

  static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
  				unsigned int event, void *data)
  {
  	switch (event) {
  	case DEVFREQ_GOV_START:
  		devfreq_monitor_start(devfreq);
  		break;
  
  	case DEVFREQ_GOV_STOP:
  		devfreq_monitor_stop(devfreq);
  		break;

  	case DEVFREQ_GOV_UPDATE_INTERVAL:
  		devfreq_update_interval(devfreq, (unsigned int *)data);

  		break;

  
  	case DEVFREQ_GOV_SUSPEND:
  		devfreq_monitor_suspend(devfreq);
  		break;
  
  	case DEVFREQ_GOV_RESUME:
  		devfreq_monitor_resume(devfreq);
  		break;

  	default:
  		break;
  	}
  
  	return 0;
  }

  static struct devfreq_governor devfreq_simple_ondemand = {

  	.name = DEVFREQ_GOV_SIMPLE_ONDEMAND,

  	.get_target_freq = devfreq_simple_ondemand_func,

  	.event_handler = devfreq_simple_ondemand_handler,

  };

  
  static int __init devfreq_simple_ondemand_init(void)
  {
  	return devfreq_add_governor(&devfreq_simple_ondemand);
  }
  subsys_initcall(devfreq_simple_ondemand_init);
  
  static void __exit devfreq_simple_ondemand_exit(void)
  {
  	int ret;
  
  	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
  	if (ret)
  		pr_err("%s: failed remove governor %d
  ", __func__, ret);
  
  	return;
  }
  module_exit(devfreq_simple_ondemand_exit);

  MODULE_LICENSE("GPL");