drivers/devfreq/governor_simpleondemand.c

   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");