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)
devfreq_simple_ondemand_func(struct devfreq * df,unsigned long * freq)21 static 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
devfreq_simple_ondemand_handler(struct devfreq * devfreq,unsigned int event,void * data)93 static 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
124 static 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
devfreq_simple_ondemand_init(void)130 static int __init devfreq_simple_ondemand_init(void)
131 {
132 return devfreq_add_governor(&devfreq_simple_ondemand);
133 }
134 subsys_initcall(devfreq_simple_ondemand_init);
135
devfreq_simple_ondemand_exit(void)136 static 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 }
146 module_exit(devfreq_simple_ondemand_exit);
147 MODULE_LICENSE("GPL");
148