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	struct devfreq_dev_status stat;
25	int err = df->profile->get_dev_status(df->dev.parent, &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	if (err)
33		return err;
34
35	if (data) {
36		if (data->upthreshold)
37			dfso_upthreshold = data->upthreshold;
38		if (data->downdifferential)
39			dfso_downdifferential = data->downdifferential;
40	}
41	if (dfso_upthreshold > 100 ||
42	    dfso_upthreshold < dfso_downdifferential)
43		return -EINVAL;
44
45	/* Assume MAX if it is going to be divided by zero */
46	if (stat.total_time == 0) {
47		*freq = max;
48		return 0;
49	}
50
51	/* Prevent overflow */
52	if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) {
53		stat.busy_time >>= 7;
54		stat.total_time >>= 7;
55	}
56
57	/* Set MAX if it's busy enough */
58	if (stat.busy_time * 100 >
59	    stat.total_time * dfso_upthreshold) {
60		*freq = max;
61		return 0;
62	}
63
64	/* Set MAX if we do not know the initial frequency */
65	if (stat.current_frequency == 0) {
66		*freq = max;
67		return 0;
68	}
69
70	/* Keep the current frequency */
71	if (stat.busy_time * 100 >
72	    stat.total_time * (dfso_upthreshold - dfso_downdifferential)) {
73		*freq = stat.current_frequency;
74		return 0;
75	}
76
77	/* Set the desired frequency based on the load */
78	a = stat.busy_time;
79	a *= stat.current_frequency;
80	b = div_u64(a, stat.total_time);
81	b *= 100;
82	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
83	*freq = (unsigned long) b;
84
85	if (df->min_freq && *freq < df->min_freq)
86		*freq = df->min_freq;
87	if (df->max_freq && *freq > df->max_freq)
88		*freq = df->max_freq;
89
90	return 0;
91}
92
93static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
94				unsigned int event, void *data)
95{
96	switch (event) {
97	case DEVFREQ_GOV_START:
98		devfreq_monitor_start(devfreq);
99		break;
100
101	case DEVFREQ_GOV_STOP:
102		devfreq_monitor_stop(devfreq);
103		break;
104
105	case DEVFREQ_GOV_INTERVAL:
106		devfreq_interval_update(devfreq, (unsigned int *)data);
107		break;
108
109	case DEVFREQ_GOV_SUSPEND:
110		devfreq_monitor_suspend(devfreq);
111		break;
112
113	case DEVFREQ_GOV_RESUME:
114		devfreq_monitor_resume(devfreq);
115		break;
116
117	default:
118		break;
119	}
120
121	return 0;
122}
123
124static struct devfreq_governor devfreq_simple_ondemand = {
125	.name = "simple_ondemand",
126	.get_target_freq = devfreq_simple_ondemand_func,
127	.event_handler = devfreq_simple_ondemand_handler,
128};
129
130static int __init devfreq_simple_ondemand_init(void)
131{
132	return devfreq_add_governor(&devfreq_simple_ondemand);
133}
134subsys_initcall(devfreq_simple_ondemand_init);
135
136static void __exit devfreq_simple_ondemand_exit(void)
137{
138	int ret;
139
140	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
141	if (ret)
142		pr_err("%s: failed remove governor %d\n", __func__, ret);
143
144	return;
145}
146module_exit(devfreq_simple_ondemand_exit);
147MODULE_LICENSE("GPL");
148