drivers/devfreq/governor_passive.c

   1 /*
   2  * linux/drivers/devfreq/governor_passive.c
   3  *
   4  * Copyright (C) 2016 Samsung Electronics
   5  * Author: Chanwoo Choi <cw00.choi@samsung.com>
   6  * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/device.h>
  15 #include <linux/devfreq.h>
  16 #include "governor.h"
  17
  18 static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
  19                                         unsigned long *freq)
  20 {
  21         struct devfreq_passive_data *p_data
  22                         = (struct devfreq_passive_data *)devfreq->data;
  23         struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
  24         unsigned long child_freq = ULONG_MAX;
  25         struct dev_pm_opp *opp;
  26         int i, count, ret = 0;
  27
  28         /*
  29          * If the devfreq device with passive governor has the specific method
  30          * to determine the next frequency, should use the get_target_freq()
  31          * of struct devfreq_passive_data.
  32          */
  33         if (p_data->get_target_freq) {
  34                 ret = p_data->get_target_freq(devfreq, freq);
  35                 goto out;
  36         }
  37
  38         /*
  39          * If the parent and passive devfreq device uses the OPP table,
  40          * get the next frequency by using the OPP table.
  41          */
  42
  43         /*
  44          * - parent devfreq device uses the governors except for passive.
  45          * - passive devfreq device uses the passive governor.
  46          *
  47          * Each devfreq has the OPP table. After deciding the new frequency
  48          * from the governor of parent devfreq device, the passive governor
  49          * need to get the index of new frequency on OPP table of parent
  50          * device. And then the index is used for getting the suitable
  51          * new frequency for passive devfreq device.
  52          */
  53         if (!devfreq->profile || !devfreq->profile->freq_table
  54                 || devfreq->profile->max_state <= 0)
  55                 return -EINVAL;
  56
  57         /*
  58          * The passive governor have to get the correct frequency from OPP
  59          * list of parent device. Because in this case, *freq is temporary
  60          * value which is decided by ondemand governor.
  61          */
  62         rcu_read_lock();
  63         opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
  64         rcu_read_unlock();
  65         if (IS_ERR(opp)) {
  66                 ret = PTR_ERR(opp);
  67                 goto out;
  68         }
  69
  70         /*
  71          * Get the OPP table's index of decided freqeuncy by governor
  72          * of parent device.
  73          */
  74         for (i = 0; i < parent_devfreq->profile->max_state; i++)
  75                 if (parent_devfreq->profile->freq_table[i] == *freq)
  76                         break;
  77
  78         if (i == parent_devfreq->profile->max_state) {
  79                 ret = -EINVAL;
  80                 goto out;
  81         }
  82
  83         /* Get the suitable frequency by using index of parent device. */
  84         if (i < devfreq->profile->max_state) {
  85                 child_freq = devfreq->profile->freq_table[i];
  86         } else {
  87                 count = devfreq->profile->max_state;
  88                 child_freq = devfreq->profile->freq_table[count - 1];
  89         }
  90
  91         /* Return the suitable frequency for passive device. */
  92         *freq = child_freq;
  93
  94 out:
  95         return ret;
  96 }
  97
  98 static int update_devfreq_passive(struct devfreq *devfreq, unsigned long freq)
  99 {
 100         int ret;
 101
 102         if (!devfreq->governor)
 103                 return -EINVAL;
 104
 105         mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
 106
 107         ret = devfreq->governor->get_target_freq(devfreq, &freq);
 108         if (ret < 0)
 109                 goto out;
 110
 111         ret = devfreq->profile->target(devfreq->dev.parent, &freq, 0);
 112         if (ret < 0)
 113                 goto out;
 114
 115         devfreq->previous_freq = freq;
 116
 117 out:
 118         mutex_unlock(&devfreq->lock);
 119
 120         return 0;
 121 }
 122
 123 static int devfreq_passive_notifier_call(struct notifier_block *nb,
 124                                 unsigned long event, void *ptr)
 125 {
 126         struct devfreq_passive_data *data
 127                         = container_of(nb, struct devfreq_passive_data, nb);
 128         struct devfreq *devfreq = (struct devfreq *)data->this;
 129         struct devfreq *parent = (struct devfreq *)data->parent;
 130         struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
 131         unsigned long freq = freqs->new;
 132
 133         switch (event) {
 134         case DEVFREQ_PRECHANGE:
 135                 if (parent->previous_freq > freq)
 136                         update_devfreq_passive(devfreq, freq);
 137                 break;
 138         case DEVFREQ_POSTCHANGE:
 139                 if (parent->previous_freq < freq)
 140                         update_devfreq_passive(devfreq, freq);
 141                 break;
 142         }
 143
 144         return NOTIFY_DONE;
 145 }
 146
 147 static int devfreq_passive_event_handler(struct devfreq *devfreq,
 148                                 unsigned int event, void *data)
 149 {
 150         struct device *dev = devfreq->dev.parent;
 151         struct devfreq_passive_data *p_data
 152                         = (struct devfreq_passive_data *)devfreq->data;
 153         struct devfreq *parent = (struct devfreq *)p_data->parent;
 154         struct notifier_block *nb = &p_data->nb;
 155         int ret = 0;
 156
 157         if (!parent)
 158                 return -EPROBE_DEFER;
 159
 160         switch (event) {
 161         case DEVFREQ_GOV_START:
 162                 if (!p_data->this)
 163                         p_data->this = devfreq;
 164
 165                 nb->notifier_call = devfreq_passive_notifier_call;
 166                 ret = devm_devfreq_register_notifier(dev, parent, nb,
 167                                         DEVFREQ_TRANSITION_NOTIFIER);
 168                 break;
 169         case DEVFREQ_GOV_STOP:
 170                 devm_devfreq_unregister_notifier(dev, parent, nb,
 171                                         DEVFREQ_TRANSITION_NOTIFIER);
 172                 break;
 173         default:
 174                 break;
 175         }
 176
 177         return ret;
 178 }
 179
 180 static struct devfreq_governor devfreq_passive = {
 181         .name = "passive",
 182         .get_target_freq = devfreq_passive_get_target_freq,
 183         .event_handler = devfreq_passive_event_handler,
 184 };
 185
 186 static int __init devfreq_passive_init(void)
 187 {
 188         return devfreq_add_governor(&devfreq_passive);
 189 }
 190 subsys_initcall(devfreq_passive_init);
 191
 192 static void __exit devfreq_passive_exit(void)
 193 {
 194         int ret;
 195
 196         ret = devfreq_remove_governor(&devfreq_passive);
 197         if (ret)
 198                 pr_err("%s: failed remove governor %d\n", __func__, ret);
 199 }
 200 module_exit(devfreq_passive_exit);
 201
 202 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
 203 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 204 MODULE_DESCRIPTION("DEVFREQ Passive governor");
 205 MODULE_LICENSE("GPL v2");