1/*
  2 *  linux/drivers/devfreq/governor_simpleondemand.c
  3 *
  4 *  Copyright (C) 2011 Samsung Electronics
  5 *	MyungJoo Ham <myungjoo.ham@samsung.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 */
 11
 12#include <linux/errno.h>
 13#include <linux/module.h>
 14#include <linux/devfreq.h>
 15#include <linux/math64.h>
 16#include "governor.h"
 17
 18/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
 19#define DFSO_UPTHRESHOLD	(90)
 20#define DFSO_DOWNDIFFERENCTIAL	(5)
 21static int devfreq_simple_ondemand_func(struct devfreq *df,
 22					unsigned long *freq)
 23{
 24	int err;
 25	struct devfreq_dev_status *stat;
 26	unsigned long long a, b;
 27	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
 28	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
 29	struct devfreq_simple_ondemand_data *data = df->data;
 30	unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
 31
 32	err = devfreq_update_stats(df);
 33	if (err)
 34		return err;
 35
 36	stat = &df->last_status;
 37
 38	if (data) {
 39		if (data->upthreshold)
 40			dfso_upthreshold = data->upthreshold;
 41		if (data->downdifferential)
 42			dfso_downdifferential = data->downdifferential;
 43	}
 44	if (dfso_upthreshold > 100 ||
 45	    dfso_upthreshold < dfso_downdifferential)
 46		return -EINVAL;
 47
 48	/* Assume MAX if it is going to be divided by zero */
 49	if (stat->total_time == 0) {
 50		*freq = max;
 51		return 0;
 52	}
 53
 54	/* Prevent overflow */
 55	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
 56		stat->busy_time >>= 7;
 57		stat->total_time >>= 7;
 58	}
 59
 60	/* Set MAX if it's busy enough */
 61	if (stat->busy_time * 100 >
 62	    stat->total_time * dfso_upthreshold) {
 63		*freq = max;
 64		return 0;
 65	}
 66
 67	/* Set MAX if we do not know the initial frequency */
 68	if (stat->current_frequency == 0) {
 69		*freq = max;
 70		return 0;
 71	}
 72
 73	/* Keep the current frequency */
 74	if (stat->busy_time * 100 >
 75	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
 76		*freq = stat->current_frequency;
 77		return 0;
 78	}
 79
 80	/* Set the desired frequency based on the load */
 81	a = stat->busy_time;
 82	a *= stat->current_frequency;
 83	b = div_u64(a, stat->total_time);
 84	b *= 100;
 85	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
 86	*freq = (unsigned long) b;
 87
 88	if (df->min_freq && *freq < df->min_freq)
 89		*freq = df->min_freq;
 90	if (df->max_freq && *freq > df->max_freq)
 91		*freq = df->max_freq;
 92
 93	return 0;
 94}
 95
 96static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
 97				unsigned int event, void *data)
 98{
 99	switch (event) {
100	case DEVFREQ_GOV_START:
101		devfreq_monitor_start(devfreq);
102		break;
103
104	case DEVFREQ_GOV_STOP:
105		devfreq_monitor_stop(devfreq);
106		break;
107
108	case DEVFREQ_GOV_INTERVAL:
109		devfreq_interval_update(devfreq, (unsigned int *)data);
110		break;
111
112	case DEVFREQ_GOV_SUSPEND:
113		devfreq_monitor_suspend(devfreq);
114		break;
115
116	case DEVFREQ_GOV_RESUME:
117		devfreq_monitor_resume(devfreq);
118		break;
119
120	default:
121		break;
122	}
123
124	return 0;
125}
126
127static struct devfreq_governor devfreq_simple_ondemand = {
128	.name = "simple_ondemand",
129	.get_target_freq = devfreq_simple_ondemand_func,
130	.event_handler = devfreq_simple_ondemand_handler,
131};
132
133static int __init devfreq_simple_ondemand_init(void)
134{
135	return devfreq_add_governor(&devfreq_simple_ondemand);
136}
137subsys_initcall(devfreq_simple_ondemand_init);
138
139static void __exit devfreq_simple_ondemand_exit(void)
140{
141	int ret;
142
143	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
144	if (ret)
145		pr_err("%s: failed remove governor %d\n", __func__, ret);
146
147	return;
148}
149module_exit(devfreq_simple_ondemand_exit);
150MODULE_LICENSE("GPL");