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 * @exit                An optional callback that is called when devfreq
  70 *                      is removing the devfreq object due to error or
  71 *                      from devfreq_remove_device() call. If the user
  72 *                      has registered devfreq->nb at a notifier-head,
  73 *                      this is the time to unregister it.
  74 */
  75struct devfreq_dev_profile {
  76        unsigned long initial_freq;
  77        unsigned int polling_ms;
  78
  79        int (*target)(struct device *dev, unsigned long *freq, u32 flags);
  80        int (*get_dev_status)(struct device *dev,
  81                              struct devfreq_dev_status *stat);
  82        void (*exit)(struct device *dev);
  83};
  84
  85/**
  86 * struct devfreq_governor - Devfreq policy governor
  87 * @name                Governor's name
  88 * @get_target_freq     Returns desired operating frequency for the device.
  89 *                      Basically, get_target_freq will run
  90 *                      devfreq_dev_profile.get_dev_status() to get the
  91 *                      status of the device (load = busy_time / total_time).
  92 *                      If no_central_polling is set, this callback is called
  93 *                      only with update_devfreq() notified by OPP.
  94 * @init                Called when the devfreq is being attached to a device
  95 * @exit                Called when the devfreq is being removed from a
  96 *                      device. Governor should stop any internal routines
  97 *                      before return because related data may be
  98 *                      freed after exit().
  99 * @no_central_polling  Do not use devfreq's central polling mechanism.
 100 *                      When this is set, devfreq will not call
 101 *                      get_target_freq with devfreq_monitor(). However,
 102 *                      devfreq will call get_target_freq with
 103 *                      devfreq_update() notified by OPP framework.
 104 *
 105 * Note that the callbacks are called with devfreq->lock locked by devfreq.
 106 */
 107struct devfreq_governor {
 108        const char name[DEVFREQ_NAME_LEN];
 109        int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
 110        int (*init)(struct devfreq *this);
 111        void (*exit)(struct devfreq *this);
 112        const bool no_central_polling;
 113};
 114
 115/**
 116 * struct devfreq - Device devfreq structure
 117 * @node        list node - contains the devices with devfreq that have been
 118 *              registered.
 119 * @lock        a mutex to protect accessing devfreq.
 120 * @dev         device registered by devfreq class. dev.parent is the device
 121 *              using devfreq.
 122 * @profile     device-specific devfreq profile
 123 * @governor    method how to choose frequency based on the usage.
 124 * @nb          notifier block used to notify devfreq object that it should
 125 *              reevaluate operable frequencies. Devfreq users may use
 126 *              devfreq.nb to the corresponding register notifier call chain.
 127 * @polling_jiffies     interval in jiffies.
 128 * @previous_freq       previously configured frequency value.
 129 * @next_polling        the number of remaining jiffies to poll with
 130 *                      "devfreq_monitor" executions to reevaluate
 131 *                      frequency/voltage of the device. Set by
 132 *                      profile's polling_ms interval.
 133 * @data        Private data of the governor. The devfreq framework does not
 134 *              touch this.
 135 * @being_removed       a flag to mark that this object is being removed in
 136 *                      order to prevent trying to remove the object multiple times.
 137 * @min_freq    Limit minimum frequency requested by user (0: none)
 138 * @max_freq    Limit maximum frequency requested by user (0: none)
 139 *
 140 * This structure stores the devfreq information for a give device.
 141 *
 142 * Note that when a governor accesses entries in struct devfreq in its
 143 * functions except for the context of callbacks defined in struct
 144 * devfreq_governor, the governor should protect its access with the
 145 * struct mutex lock in struct devfreq. A governor may use this mutex
 146 * to protect its own private data in void *data as well.
 147 */
 148struct devfreq {
 149        struct list_head node;
 150
 151        struct mutex lock;
 152        struct device dev;
 153        struct devfreq_dev_profile *profile;
 154        const struct devfreq_governor *governor;
 155        struct notifier_block nb;
 156
 157        unsigned long polling_jiffies;
 158        unsigned long previous_freq;
 159        unsigned int next_polling;
 160
 161        void *data; /* private data for governors */
 162
 163        bool being_removed;
 164
 165        unsigned long min_freq;
 166        unsigned long max_freq;
 167};
 168
 169#if defined(CONFIG_PM_DEVFREQ)
 170extern struct devfreq *devfreq_add_device(struct device *dev,
 171                                  struct devfreq_dev_profile *profile,
 172                                  const struct devfreq_governor *governor,
 173                                  void *data);
 174extern int devfreq_remove_device(struct devfreq *devfreq);
 175
 176/* Helper functions for devfreq user device driver with OPP. */
 177extern struct opp *devfreq_recommended_opp(struct device *dev,
 178                                           unsigned long *freq, u32 flags);
 179extern int devfreq_register_opp_notifier(struct device *dev,
 180                                         struct devfreq *devfreq);
 181extern int devfreq_unregister_opp_notifier(struct device *dev,
 182                                           struct devfreq *devfreq);
 183
 184#ifdef CONFIG_DEVFREQ_GOV_POWERSAVE
 185extern const struct devfreq_governor devfreq_powersave;
 186#endif
 187#ifdef CONFIG_DEVFREQ_GOV_PERFORMANCE
 188extern const struct devfreq_governor devfreq_performance;
 189#endif
 190#ifdef CONFIG_DEVFREQ_GOV_USERSPACE
 191extern const struct devfreq_governor devfreq_userspace;
 192#endif
 193#ifdef CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND
 194extern const struct devfreq_governor devfreq_simple_ondemand;
 195/**
 196 * struct devfreq_simple_ondemand_data - void *data fed to struct devfreq
 197 *      and devfreq_add_device
 198 * @ upthreshold        If the load is over this value, the frequency jumps.
 199 *                      Specify 0 to use the default. Valid value = 0 to 100.
 200 * @ downdifferential   If the load is under upthreshold - downdifferential,
 201 *                      the governor may consider slowing the frequency down.
 202 *                      Specify 0 to use the default. Valid value = 0 to 100.
 203 *                      downdifferential < upthreshold must hold.
 204 *
 205 * If the fed devfreq_simple_ondemand_data pointer is NULL to the governor,
 206 * the governor uses the default values.
 207 */
 208struct devfreq_simple_ondemand_data {
 209        unsigned int upthreshold;
 210        unsigned int downdifferential;
 211};
 212#endif
 213
 214#else /* !CONFIG_PM_DEVFREQ */
 215static struct devfreq *devfreq_add_device(struct device *dev,
 216                                          struct devfreq_dev_profile *profile,
 217                                          struct devfreq_governor *governor,
 218                                          void *data)
 219{
 220        return NULL;
 221}
 222
 223static int devfreq_remove_device(struct devfreq *devfreq)
 224{
 225        return 0;
 226}
 227
 228static struct opp *devfreq_recommended_opp(struct device *dev,
 229                                           unsigned long *freq, u32 flags)
 230{
 231        return -EINVAL;
 232}
 233
 234static int devfreq_register_opp_notifier(struct device *dev,
 235                                         struct devfreq *devfreq)
 236{
 237        return -EINVAL;
 238}
 239
 240static int devfreq_unregister_opp_notifier(struct device *dev,
 241                                           struct devfreq *devfreq)
 242{
 243        return -EINVAL;
 244}
 245
 246#define devfreq_powersave       NULL
 247#define devfreq_performance     NULL
 248#define devfreq_userspace       NULL
 249#define devfreq_simple_ondemand NULL
 250
 251#endif /* CONFIG_PM_DEVFREQ */
 252
 253#endif /* __LINUX_DEVFREQ_H__ */
 254
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