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         int err;
  25         struct devfreq_dev_status *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         err = devfreq_update_stats(df);
  33         if (err)
  34                 return err;
  35
  36         stat = &df->last_status;
  37
  38         if (data) {
  39                 if (data->upthreshold)
  40                         dfso_upthreshold = data->upthreshold;
  41                 if (data->downdifferential)
  42                         dfso_downdifferential = data->downdifferential;
  43         }
  44         if (dfso_upthreshold > 100 ||
  45             dfso_upthreshold < dfso_downdifferential)
  46                 return -EINVAL;
  47
  48         /* Assume MAX if it is going to be divided by zero */
  49         if (stat->total_time == 0) {
  50                 *freq = max;
  51                 return 0;
  52         }
  53
  54         /* Prevent overflow */
  55         if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
  56                 stat->busy_time >>= 7;
  57                 stat->total_time >>= 7;
  58         }
  59
  60         /* Set MAX if it's busy enough */
  61         if (stat->busy_time * 100 >
  62             stat->total_time * dfso_upthreshold) {
  63                 *freq = max;
  64                 return 0;
  65         }
  66
  67         /* Set MAX if we do not know the initial frequency */
  68         if (stat->current_frequency == 0) {
  69                 *freq = max;
  70                 return 0;
  71         }
  72
  73         /* Keep the current frequency */
  74         if (stat->busy_time * 100 >
  75             stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
  76                 *freq = stat->current_frequency;
  77                 return 0;
  78         }
  79
  80         /* Set the desired frequency based on the load */
  81         a = stat->busy_time;
  82         a *= stat->current_frequency;
  83         b = div_u64(a, stat->total_time);
  84         b *= 100;
  85         b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
  86         *freq = (unsigned long) b;
  87
  88         if (df->min_freq && *freq < df->min_freq)
  89                 *freq = df->min_freq;
  90         if (df->max_freq && *freq > df->max_freq)
  91                 *freq = df->max_freq;
  92
  93         return 0;
  94 }
  95
  96 static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
  97                                 unsigned int event, void *data)
  98 {
  99         switch (event) {
 100         case DEVFREQ_GOV_START:
 101                 devfreq_monitor_start(devfreq);
 102                 break;
 103
 104         case DEVFREQ_GOV_STOP:
 105                 devfreq_monitor_stop(devfreq);
 106                 break;
 107
 108         case DEVFREQ_GOV_INTERVAL:
 109                 devfreq_interval_update(devfreq, (unsigned int *)data);
 110                 break;
 111
 112         case DEVFREQ_GOV_SUSPEND:
 113                 devfreq_monitor_suspend(devfreq);
 114                 break;
 115
 116         case DEVFREQ_GOV_RESUME:
 117                 devfreq_monitor_resume(devfreq);
 118                 break;
 119
 120         default:
 121                 break;
 122         }
 123
 124         return 0;
 125 }
 126
 127 static struct devfreq_governor devfreq_simple_ondemand = {
 128         .name = "simple_ondemand",
 129         .get_target_freq = devfreq_simple_ondemand_func,
 130         .event_handler = devfreq_simple_ondemand_handler,
 131 };
 132
 133 static int __init devfreq_simple_ondemand_init(void)
 134 {
 135         return devfreq_add_governor(&devfreq_simple_ondemand);
 136 }
 137 subsys_initcall(devfreq_simple_ondemand_init);
 138
 139 static void __exit devfreq_simple_ondemand_exit(void)
 140 {
 141         int ret;
 142
 143         ret = devfreq_remove_governor(&devfreq_simple_ondemand);
 144         if (ret)
 145                 pr_err("%s: failed remove governor %d\n", __func__, ret);
 146
 147         return;
 148 }
 149 module_exit(devfreq_simple_ondemand_exit);
 150 MODULE_LICENSE("GPL");