aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/devfreq/governor_simpleondemand.c
blob: 28e0f2de7100ee0cee83b1e1179c750694b942af (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
/*
 *  linux/drivers/devfreq/governor_simpleondemand.c
 *
 *  Copyright (C) 2011 Samsung Electronics
 *	MyungJoo Ham <myungjoo.ham@samsung.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#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;
	unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;

	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 = max;
		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 = max;
		return 0;
	}

	/* Set MAX if we do not know the initial frequency */
	if (stat->current_frequency == 0) {
		*freq = max;
		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;

	if (df->min_freq && *freq < df->min_freq)
		*freq = df->min_freq;
	if (df->max_freq && *freq > df->max_freq)
		*freq = df->max_freq;

	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_INTERVAL:
		devfreq_interval_update(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\n", __func__, ret);

	return;
}
module_exit(devfreq_simple_ondemand_exit);
MODULE_LICENSE("GPL");

Privacy Policy