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) |
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(dividend: a, divisor: stat->total_time); |
80 | b *= 100; |
81 | b = div_u64(dividend: b, divisor: (dfso_upthreshold - dfso_downdifferential / 2)); |
82 | *freq = (unsigned long) b; |
83 | |
84 | return 0; |
85 | } |
86 | |
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, delay: (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 | |
126 | static int __init devfreq_simple_ondemand_init(void) |
127 | { |
128 | return devfreq_add_governor(governor: &devfreq_simple_ondemand); |
129 | } |
130 | subsys_initcall(devfreq_simple_ondemand_init); |
131 | |
132 | static void __exit devfreq_simple_ondemand_exit(void) |
133 | { |
134 | int ret; |
135 | |
136 | ret = devfreq_remove_governor(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 | |