linux/include/linux/devfreq.h
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   1/*
   2 * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
   3 *          for Non-CPU Devices.
   4 *
   5 * Copyright (C) 2011 Samsung Electronics
   6 *      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#ifndef __LINUX_DEVFREQ_H__
  14#define __LINUX_DEVFREQ_H__
  15
  16#include <linux/device.h>
  17#include <linux/notifier.h>
  18#include <linux/opp.h>
  19
  20#define DEVFREQ_NAME_LEN 16
  21
  22struct devfreq;
  23
  24/**
  25 * struct devfreq_dev_status - Data given from devfreq user device to
  26 *                           governors. Represents the performance
  27 *                           statistics.
  28 * @total_time:         The total time represented by this instance of
  29 *                      devfreq_dev_status
  30 * @busy_time:          The time that the device was working among the
  31 *                      total_time.
  32 * @current_frequency:  The operating frequency.
  33 * @private_data:       An entry not specified by the devfreq framework.
  34 *                      A device and a specific governor may have their
  35 *                      own protocol with private_data. However, because
  36 *                      this is governor-specific, a governor using this
  37 *                      will be only compatible with devices aware of it.
  38 */
  39struct devfreq_dev_status {
  40        /* both since the last measure */
  41        unsigned long total_time;
  42        unsigned long busy_time;
  43        unsigned long current_frequency;
  44        void *private_data;
  45};
  46
  47/*
  48 * The resulting frequency should be at most this. (this bound is the
  49 * least upper bound; thus, the resulting freq should be lower or same)
  50 * If the flag is not set, the resulting frequency should be at most the
  51 * bound (greatest lower bound)
  52 */
  53#define DEVFREQ_FLAG_LEAST_UPPER_BOUND          0x1
  54
  55/**
  56 * struct devfreq_dev_profile - Devfreq's user device profile
  57 * @initial_freq:       The operating frequency when devfreq_add_device() is
  58 *                      called.
  59 * @polling_ms:         The polling interval in ms. 0 disables polling.
  60 * @target:             The device should set its operating frequency at
  61 *                      freq or lowest-upper-than-freq value. If freq is
  62 *                      higher than any operable frequency, set maximum.
  63 *                      Before returning, target function should set
  64 *                      freq at the current frequency.
  65 *                      The "flags" parameter's possible values are
  66 *                      explained above with "DEVFREQ_FLAG_*" macros.
  67 * @get_dev_status:     The device should provide the current performance
  68 *                      status to devfreq, which is used by governors.
  69 * @get_cur_freq:       The device should provide the current frequency
  70 *                      at which it is operating.
  71 * @exit:               An optional callback that is called when devfreq
  72 *                      is removing the devfreq object due to error or
  73 *                      from devfreq_remove_device() call. If the user
  74 *                      has registered devfreq->nb at a notifier-head,
  75 *                      this is the time to unregister it.
  76 * @freq_table: Optional list of frequencies to support statistics.
  77 * @max_state:  The size of freq_table.
  78 */
  79struct devfreq_dev_profile {
  80        unsigned long initial_freq;
  81        unsigned int polling_ms;
  82
  83        int (*target)(struct device *dev, unsigned long *freq, u32 flags);
  84        int (*get_dev_status)(struct device *dev,
  85                              struct devfreq_dev_status *stat);
  86        int (*get_cur_freq)(struct device *dev, unsigned long *freq);
  87        void (*exit)(struct device *dev);
  88
  89        unsigned int *freq_table;
  90        unsigned int max_state;
  91};
  92
  93/**
  94 * struct devfreq_governor - Devfreq policy governor
  95 * @node:               list node - contains registered devfreq governors
  96 * @name:               Governor's name
  97 * @get_target_freq:    Returns desired operating frequency for the device.
  98 *                      Basically, get_target_freq will run
  99 *                      devfreq_dev_profile.get_dev_status() to get the
 100 *                      status of the device (load = busy_time / total_time).
 101 *                      If no_central_polling is set, this callback is called
 102 *                      only with update_devfreq() notified by OPP.
 103 * @event_handler:      Callback for devfreq core framework to notify events
 104 *                      to governors. Events include per device governor
 105 *                      init and exit, opp changes out of devfreq, suspend
 106 *                      and resume of per device devfreq during device idle.
 107 *
 108 * Note that the callbacks are called with devfreq->lock locked by devfreq.
 109 */
 110struct devfreq_governor {
 111        struct list_head node;
 112
 113        const char name[DEVFREQ_NAME_LEN];
 114        int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
 115        int (*event_handler)(struct devfreq *devfreq,
 116                                unsigned int event, void *data);
 117};
 118
 119/**
 120 * struct devfreq - Device devfreq structure
 121 * @node:       list node - contains the devices with devfreq that have been
 122 *              registered.
 123 * @lock:       a mutex to protect accessing devfreq.
 124 * @dev:        device registered by devfreq class. dev.parent is the device
 125 *              using devfreq.
 126 * @profile:    device-specific devfreq profile
 127 * @governor:   method how to choose frequency based on the usage.
 128 * @governor_name:      devfreq governor name for use with this devfreq
 129 * @nb:         notifier block used to notify devfreq object that it should
 130 *              reevaluate operable frequencies. Devfreq users may use
 131 *              devfreq.nb to the corresponding register notifier call chain.
 132 * @work:       delayed work for load monitoring.
 133 * @previous_freq:      previously configured frequency value.
 134 * @data:       Private data of the governor. The devfreq framework does not
 135 *              touch this.
 136 * @min_freq:   Limit minimum frequency requested by user (0: none)
 137 * @max_freq:   Limit maximum frequency requested by user (0: none)
 138 * @stop_polling:        devfreq polling status of a device.
 139 * @total_trans:        Number of devfreq transitions
 140 * @trans_table:        Statistics of devfreq transitions
 141 * @time_in_state:      Statistics of devfreq states
 142 * @last_stat_updated:  The last time stat updated
 143 *
 144 * This structure stores the devfreq information for a give device.
 145 *
 146 * Note that when a governor accesses entries in struct devfreq in its
 147 * functions except for the context of callbacks defined in struct
 148 * devfreq_governor, the governor should protect its access with the
 149 * struct mutex lock in struct devfreq. A governor may use this mutex
 150 * to protect its own private data in void *data as well.
 151 */
 152struct devfreq {
 153        struct list_head node;
 154
 155        struct mutex lock;
 156        struct device dev;
 157        struct devfreq_dev_profile *profile;
 158        const struct devfreq_governor *governor;
 159        char governor_name[DEVFREQ_NAME_LEN];
 160        struct notifier_block nb;
 161        struct delayed_work work;
 162
 163        unsigned long previous_freq;
 164
 165        void *data; /* private data for governors */
 166
 167        unsigned long min_freq;
 168        unsigned long max_freq;
 169        bool stop_polling;
 170
 171        /* information for device freqeuncy transition */
 172        unsigned int total_trans;
 173        unsigned int *trans_table;
 174        unsigned long *time_in_state;
 175        unsigned long last_stat_updated;
 176};
 177
 178#if defined(CONFIG_PM_DEVFREQ)
 179extern struct devfreq *devfreq_add_device(struct device *dev,
 180                                  struct devfreq_dev_profile *profile,
 181                                  const char *governor_name,
 182                                  void *data);
 183extern int devfreq_remove_device(struct devfreq *devfreq);
 184extern int devfreq_suspend_device(struct devfreq *devfreq);
 185extern int devfreq_resume_device(struct devfreq *devfreq);
 186
 187/* Helper functions for devfreq user device driver with OPP. */
 188extern struct opp *devfreq_recommended_opp(struct device *dev,
 189                                           unsigned long *freq, u32 flags);
 190extern int devfreq_register_opp_notifier(struct device *dev,
 191                                         struct devfreq *devfreq);
 192extern int devfreq_unregister_opp_notifier(struct device *dev,
 193                                           struct devfreq *devfreq);
 194
 195#if IS_ENABLED(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)
 196/**
 197 * struct devfreq_simple_ondemand_data - void *data fed to struct devfreq
 198 *      and devfreq_add_device
 199 * @upthreshold:        If the load is over this value, the frequency jumps.
 200 *                      Specify 0 to use the default. Valid value = 0 to 100.
 201 * @downdifferential:   If the load is under upthreshold - downdifferential,
 202 *                      the governor may consider slowing the frequency down.
 203 *                      Specify 0 to use the default. Valid value = 0 to 100.
 204 *                      downdifferential < upthreshold must hold.
 205 *
 206 * If the fed devfreq_simple_ondemand_data pointer is NULL to the governor,
 207 * the governor uses the default values.
 208 */
 209struct devfreq_simple_ondemand_data {
 210        unsigned int upthreshold;
 211        unsigned int downdifferential;
 212};
 213#endif
 214
 215#else /* !CONFIG_PM_DEVFREQ */
 216static struct devfreq *devfreq_add_device(struct device *dev,
 217                                          struct devfreq_dev_profile *profile,
 218                                          const char *governor_name,
 219                                          void *data)
 220{
 221        return NULL;
 222}
 223
 224static int devfreq_remove_device(struct devfreq *devfreq)
 225{
 226        return 0;
 227}
 228
 229static int devfreq_suspend_device(struct devfreq *devfreq)
 230{
 231        return 0;
 232}
 233
 234static int devfreq_resume_device(struct devfreq *devfreq)
 235{
 236        return 0;
 237}
 238
 239static struct opp *devfreq_recommended_opp(struct device *dev,
 240                                           unsigned long *freq, u32 flags)
 241{
 242        return -EINVAL;
 243}
 244
 245static int devfreq_register_opp_notifier(struct device *dev,
 246                                         struct devfreq *devfreq)
 247{
 248        return -EINVAL;
 249}
 250
 251static int devfreq_unregister_opp_notifier(struct device *dev,
 252                                           struct devfreq *devfreq)
 253{
 254        return -EINVAL;
 255}
 256
 257#endif /* CONFIG_PM_DEVFREQ */
 258
 259#endif /* __LINUX_DEVFREQ_H__ */
 260
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