drivers/devfreq/governor_passive.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/drivers/devfreq/governor_passive.c
   4  *
   5  * Copyright (C) 2016 Samsung Electronics
   6  * Author: Chanwoo Choi <cw00.choi@samsung.com>
   7  * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/device.h>
  12 #include <linux/devfreq.h>
  13 #include "governor.h"
  14
  15 static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
  16                                         unsigned long *freq)
  17 {
  18         struct devfreq_passive_data *p_data
  19                         = (struct devfreq_passive_data *)devfreq->data;
  20         struct devfreq *parent_devfreq = (struct devfreq *)p_data->parent;
  21         unsigned long child_freq = ULONG_MAX;
  22         struct dev_pm_opp *opp;
  23         int i, count, ret = 0;
  24
  25         /*
  26          * If the devfreq device with passive governor has the specific method
  27          * to determine the next frequency, should use the get_target_freq()
  28          * of struct devfreq_passive_data.
  29          */
  30         if (p_data->get_target_freq) {
  31                 ret = p_data->get_target_freq(devfreq, freq);
  32                 goto out;
  33         }
  34
  35         /*
  36          * If the parent and passive devfreq device uses the OPP table,
  37          * get the next frequency by using the OPP table.
  38          */
  39
  40         /*
  41          * - parent devfreq device uses the governors except for passive.
  42          * - passive devfreq device uses the passive governor.
  43          *
  44          * Each devfreq has the OPP table. After deciding the new frequency
  45          * from the governor of parent devfreq device, the passive governor
  46          * need to get the index of new frequency on OPP table of parent
  47          * device. And then the index is used for getting the suitable
  48          * new frequency for passive devfreq device.
  49          */
  50         if (!devfreq->profile || !devfreq->profile->freq_table
  51                 || devfreq->profile->max_state <= 0)
  52                 return -EINVAL;
  53
  54         /*
  55          * The passive governor have to get the correct frequency from OPP
  56          * list of parent device. Because in this case, *freq is temporary
  57          * value which is decided by ondemand governor.
  58          */
  59         opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
  60         if (IS_ERR(opp)) {
  61                 ret = PTR_ERR(opp);
  62                 goto out;
  63         }
  64
  65         dev_pm_opp_put(opp);
  66
  67         /*
  68          * Get the OPP table's index of decided freqeuncy by governor
  69          * of parent device.
  70          */
  71         for (i = 0; i < parent_devfreq->profile->max_state; i++)
  72                 if (parent_devfreq->profile->freq_table[i] == *freq)
  73                         break;
  74
  75         if (i == parent_devfreq->profile->max_state) {
  76                 ret = -EINVAL;
  77                 goto out;
  78         }
  79
  80         /* Get the suitable frequency by using index of parent device. */
  81         if (i < devfreq->profile->max_state) {
  82                 child_freq = devfreq->profile->freq_table[i];
  83         } else {
  84                 count = devfreq->profile->max_state;
  85                 child_freq = devfreq->profile->freq_table[count - 1];
  86         }
  87
  88         /* Return the suitable frequency for passive device. */
  89         *freq = child_freq;
  90
  91 out:
  92         return ret;
  93 }
  94
  95 static int devfreq_passive_notifier_call(struct notifier_block *nb,
  96                                 unsigned long event, void *ptr)
  97 {
  98         struct devfreq_passive_data *data
  99                         = container_of(nb, struct devfreq_passive_data, nb);
 100         struct devfreq *devfreq = (struct devfreq *)data->this;
 101         struct devfreq *parent = (struct devfreq *)data->parent;
 102         struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
 103         unsigned long freq = freqs->new;
 104         int ret = 0;
 105
 106         mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
 107         switch (event) {
 108         case DEVFREQ_PRECHANGE:
 109                 if (parent->previous_freq > freq)
 110                         ret = devfreq_update_target(devfreq, freq);
 111
 112                 break;
 113         case DEVFREQ_POSTCHANGE:
 114                 if (parent->previous_freq < freq)
 115                         ret = devfreq_update_target(devfreq, freq);
 116                 break;
 117         }
 118         mutex_unlock(&devfreq->lock);
 119
 120         if (ret < 0)
 121                 dev_warn(&devfreq->dev,
 122                         "failed to update devfreq using passive governor\n");
 123
 124         return NOTIFY_DONE;
 125 }
 126
 127 static int devfreq_passive_event_handler(struct devfreq *devfreq,
 128                                 unsigned int event, void *data)
 129 {
 130         struct devfreq_passive_data *p_data
 131                         = (struct devfreq_passive_data *)devfreq->data;
 132         struct devfreq *parent = (struct devfreq *)p_data->parent;
 133         struct notifier_block *nb = &p_data->nb;
 134         int ret = 0;
 135
 136         if (!parent)
 137                 return -EPROBE_DEFER;
 138
 139         switch (event) {
 140         case DEVFREQ_GOV_START:
 141                 if (!p_data->this)
 142                         p_data->this = devfreq;
 143
 144                 nb->notifier_call = devfreq_passive_notifier_call;
 145                 ret = devfreq_register_notifier(parent, nb,
 146                                         DEVFREQ_TRANSITION_NOTIFIER);
 147                 break;
 148         case DEVFREQ_GOV_STOP:
 149                 WARN_ON(devfreq_unregister_notifier(parent, nb,
 150                                         DEVFREQ_TRANSITION_NOTIFIER));
 151                 break;
 152         default:
 153                 break;
 154         }
 155
 156         return ret;
 157 }
 158
 159 static struct devfreq_governor devfreq_passive = {
 160         .name = DEVFREQ_GOV_PASSIVE,
 161         .flags = DEVFREQ_GOV_FLAG_IMMUTABLE,
 162         .get_target_freq = devfreq_passive_get_target_freq,
 163         .event_handler = devfreq_passive_event_handler,
 164 };
 165
 166 static int __init devfreq_passive_init(void)
 167 {
 168         return devfreq_add_governor(&devfreq_passive);
 169 }
 170 subsys_initcall(devfreq_passive_init);
 171
 172 static void __exit devfreq_passive_exit(void)
 173 {
 174         int ret;
 175
 176         ret = devfreq_remove_governor(&devfreq_passive);
 177         if (ret)
 178                 pr_err("%s: failed remove governor %d\n", __func__, ret);
 179 }
 180 module_exit(devfreq_passive_exit);
 181
 182 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
 183 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 184 MODULE_DESCRIPTION("DEVFREQ Passive governor");
 185 MODULE_LICENSE("GPL v2");