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