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, *p_opp;
  23         int i, count;
  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                 return p_data->get_target_freq(devfreq, freq);
  32
  33         /*
  34          * If the parent and passive devfreq device uses the OPP table,
  35          * get the next frequency by using the OPP table.
  36          */
  37
  38         /*
  39          * - parent devfreq device uses the governors except for passive.
  40          * - passive devfreq device uses the passive governor.
  41          *
  42          * Each devfreq has the OPP table. After deciding the new frequency
  43          * from the governor of parent devfreq device, the passive governor
  44          * need to get the index of new frequency on OPP table of parent
  45          * device. And then the index is used for getting the suitable
  46          * new frequency for passive devfreq device.
  47          */
  48         if (!devfreq->profile || !devfreq->profile->freq_table
  49                 || devfreq->profile->max_state <= 0)
  50                 return -EINVAL;
  51
  52         /*
  53          * The passive governor have to get the correct frequency from OPP
  54          * list of parent device. Because in this case, *freq is temporary
  55          * value which is decided by ondemand governor.
  56          */
  57         if (devfreq->opp_table && parent_devfreq->opp_table) {
  58                 p_opp = devfreq_recommended_opp(parent_devfreq->dev.parent,
  59                                                 freq, 0);
  60                 if (IS_ERR(p_opp))
  61                         return PTR_ERR(p_opp);
  62
  63                 opp = dev_pm_opp_xlate_required_opp(parent_devfreq->opp_table,
  64                                                     devfreq->opp_table, p_opp);
  65                 dev_pm_opp_put(p_opp);
  66
  67                 if (IS_ERR(opp))
  68                         goto no_required_opp;
  69
  70                 *freq = dev_pm_opp_get_freq(opp);
  71                 dev_pm_opp_put(opp);
  72
  73                 return 0;
  74         }
  75
  76 no_required_opp:
  77         /*
  78          * Get the OPP table's index of decided frequency by governor
  79          * of parent device.
  80          */
  81         for (i = 0; i < parent_devfreq->profile->max_state; i++)
  82                 if (parent_devfreq->profile->freq_table[i] == *freq)
  83                         break;
  84
  85         if (i == parent_devfreq->profile->max_state)
  86                 return -EINVAL;
  87
  88         /* Get the suitable frequency by using index of parent device. */
  89         if (i < devfreq->profile->max_state) {
  90                 child_freq = devfreq->profile->freq_table[i];
  91         } else {
  92                 count = devfreq->profile->max_state;
  93                 child_freq = devfreq->profile->freq_table[count - 1];
  94         }
  95
  96         /* Return the suitable frequency for passive device. */
  97         *freq = child_freq;
  98
  99         return 0;
 100 }
 101
 102 static int devfreq_passive_notifier_call(struct notifier_block *nb,
 103                                 unsigned long event, void *ptr)
 104 {
 105         struct devfreq_passive_data *data
 106                         = container_of(nb, struct devfreq_passive_data, nb);
 107         struct devfreq *devfreq = (struct devfreq *)data->this;
 108         struct devfreq *parent = (struct devfreq *)data->parent;
 109         struct devfreq_freqs *freqs = (struct devfreq_freqs *)ptr;
 110         unsigned long freq = freqs->new;
 111         int ret = 0;
 112
 113         mutex_lock_nested(&devfreq->lock, SINGLE_DEPTH_NESTING);
 114         switch (event) {
 115         case DEVFREQ_PRECHANGE:
 116                 if (parent->previous_freq > freq)
 117                         ret = devfreq_update_target(devfreq, freq);
 118
 119                 break;
 120         case DEVFREQ_POSTCHANGE:
 121                 if (parent->previous_freq < freq)
 122                         ret = devfreq_update_target(devfreq, freq);
 123                 break;
 124         }
 125         mutex_unlock(&devfreq->lock);
 126
 127         if (ret < 0)
 128                 dev_warn(&devfreq->dev,
 129                         "failed to update devfreq using passive governor\n");
 130
 131         return NOTIFY_DONE;
 132 }
 133
 134 static int devfreq_passive_event_handler(struct devfreq *devfreq,
 135                                 unsigned int event, void *data)
 136 {
 137         struct devfreq_passive_data *p_data
 138                         = (struct devfreq_passive_data *)devfreq->data;
 139         struct devfreq *parent = (struct devfreq *)p_data->parent;
 140         struct notifier_block *nb = &p_data->nb;
 141         int ret = 0;
 142
 143         if (!parent)
 144                 return -EPROBE_DEFER;
 145
 146         switch (event) {
 147         case DEVFREQ_GOV_START:
 148                 if (!p_data->this)
 149                         p_data->this = devfreq;
 150
 151                 nb->notifier_call = devfreq_passive_notifier_call;
 152                 ret = devfreq_register_notifier(parent, nb,
 153                                         DEVFREQ_TRANSITION_NOTIFIER);
 154                 break;
 155         case DEVFREQ_GOV_STOP:
 156                 WARN_ON(devfreq_unregister_notifier(parent, nb,
 157                                         DEVFREQ_TRANSITION_NOTIFIER));
 158                 break;
 159         default:
 160                 break;
 161         }
 162
 163         return ret;
 164 }
 165
 166 static struct devfreq_governor devfreq_passive = {
 167         .name = DEVFREQ_GOV_PASSIVE,
 168         .flags = DEVFREQ_GOV_FLAG_IMMUTABLE,
 169         .get_target_freq = devfreq_passive_get_target_freq,
 170         .event_handler = devfreq_passive_event_handler,
 171 };
 172
 173 static int __init devfreq_passive_init(void)
 174 {
 175         return devfreq_add_governor(&devfreq_passive);
 176 }
 177 subsys_initcall(devfreq_passive_init);
 178
 179 static void __exit devfreq_passive_exit(void)
 180 {
 181         int ret;
 182
 183         ret = devfreq_remove_governor(&devfreq_passive);
 184         if (ret)
 185                 pr_err("%s: failed remove governor %d\n", __func__, ret);
 186 }
 187 module_exit(devfreq_passive_exit);
 188
 189 MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
 190 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 191 MODULE_DESCRIPTION("DEVFREQ Passive governor");
 192 MODULE_LICENSE("GPL v2");