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