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)
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 
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 
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 
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