1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/drivers/devfreq/governor_simpleondemand.c
4 *
5 * Copyright (C) 2011 Samsung Electronics
6 * MyungJoo Ham <myungjoo.ham@samsung.com>
7 */
8
9 #include <linux/errno.h>
10 #include <linux/module.h>
11 #include <linux/devfreq.h>
12 #include <linux/math64.h>
13 #include "governor.h"
14
15 /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
16 #define DFSO_UPTHRESHOLD (90)
17 #define DFSO_DOWNDIFFERENCTIAL (5)
devfreq_simple_ondemand_func(struct devfreq * df,unsigned long * freq)18 static int devfreq_simple_ondemand_func(struct devfreq *df,
19 unsigned long *freq)
20 {
21 int err;
22 struct devfreq_dev_status *stat;
23 unsigned long long a, b;
24 unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
25 unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
26 struct devfreq_simple_ondemand_data *data = df->data;
27
28 err = devfreq_update_stats(df);
29 if (err)
30 return err;
31
32 stat = &df->last_status;
33
34 if (data) {
35 if (data->upthreshold)
36 dfso_upthreshold = data->upthreshold;
37 if (data->downdifferential)
38 dfso_downdifferential = data->downdifferential;
39 }
40 if (dfso_upthreshold > 100 ||
41 dfso_upthreshold < dfso_downdifferential)
42 return -EINVAL;
43
44 /* Assume MAX if it is going to be divided by zero */
45 if (stat->total_time == 0) {
46 *freq = DEVFREQ_MAX_FREQ;
47 return 0;
48 }
49
50 /* Prevent overflow */
51 if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
52 stat->busy_time >>= 7;
53 stat->total_time >>= 7;
54 }
55
56 /* Set MAX if it's busy enough */
57 if (stat->busy_time * 100 >
58 stat->total_time * dfso_upthreshold) {
59 *freq = DEVFREQ_MAX_FREQ;
60 return 0;
61 }
62
63 /* Set MAX if we do not know the initial frequency */
64 if (stat->current_frequency == 0) {
65 *freq = DEVFREQ_MAX_FREQ;
66 return 0;
67 }
68
69 /* Keep the current frequency */
70 if (stat->busy_time * 100 >
71 stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
72 *freq = stat->current_frequency;
73 return 0;
74 }
75
76 /* Set the desired frequency based on the load */
77 a = stat->busy_time;
78 a *= stat->current_frequency;
79 b = div_u64(a, stat->total_time);
80 b *= 100;
81 b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
82 *freq = (unsigned long) b;
83
84 return 0;
85 }
86
devfreq_simple_ondemand_handler(struct devfreq * devfreq,unsigned int event,void * data)87 static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
88 unsigned int event, void *data)
89 {
90 switch (event) {
91 case DEVFREQ_GOV_START:
92 devfreq_monitor_start(devfreq);
93 break;
94
95 case DEVFREQ_GOV_STOP:
96 devfreq_monitor_stop(devfreq);
97 break;
98
99 case DEVFREQ_GOV_UPDATE_INTERVAL:
100 devfreq_update_interval(devfreq, (unsigned int *)data);
101 break;
102
103 case DEVFREQ_GOV_SUSPEND:
104 devfreq_monitor_suspend(devfreq);
105 break;
106
107 case DEVFREQ_GOV_RESUME:
108 devfreq_monitor_resume(devfreq);
109 break;
110
111 default:
112 break;
113 }
114
115 return 0;
116 }
117
118 static struct devfreq_governor devfreq_simple_ondemand = {
119 .name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
120 .attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
121 | DEVFREQ_GOV_ATTR_TIMER,
122 .get_target_freq = devfreq_simple_ondemand_func,
123 .event_handler = devfreq_simple_ondemand_handler,
124 };
125
devfreq_simple_ondemand_init(void)126 static int __init devfreq_simple_ondemand_init(void)
127 {
128 return devfreq_add_governor(&devfreq_simple_ondemand);
129 }
130 subsys_initcall(devfreq_simple_ondemand_init);
131
devfreq_simple_ondemand_exit(void)132 static void __exit devfreq_simple_ondemand_exit(void)
133 {
134 int ret;
135
136 ret = devfreq_remove_governor(&devfreq_simple_ondemand);
137 if (ret)
138 pr_err("%s: failed remove governor %d\n", __func__, ret);
139
140 return;
141 }
142 module_exit(devfreq_simple_ondemand_exit);
143 MODULE_LICENSE("GPL");
144