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/*

 *  drivers/cpufreq/cpufreq_conservative.c

 *

 *  Copyright (C)  2001 Russell King

 *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.

 *                      Jun Nakajima <jun.nakajima@intel.com>

 *            (C)  2004 Alexander Clouter <alex-kernel@digriz.org.uk>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/smp.h>

#include <linux/init.h>

#include <linux/interrupt.h>

#include <linux/ctype.h>

#include <linux/cpufreq.h>

#include <linux/sysctl.h>

#include <linux/types.h>

#include <linux/fs.h>

#include <linux/sysfs.h>

#include <linux/cpu.h>

#include <linux/kmod.h>

#include <linux/workqueue.h>

#include <linux/jiffies.h>

#include <linux/kernel_stat.h>

#include <linux/percpu.h>

#include <linux/mutex.h>

/*

 * dbs is used in this file as a shortform for demandbased switching

 * It helps to keep variable names smaller, simpler

 */

#define DEF_FREQUENCY_UP_THRESHOLD              (80)

#define DEF_FREQUENCY_DOWN_THRESHOLD            (20)

/*

 * The polling frequency of this governor depends on the capability of

 * the processor. Default polling frequency is 1000 times the transition

 * latency of the processor. The governor will work on any processor with

 * transition latency <= 10mS, using appropriate sampling

 * rate.

 * For CPUs with transition latency > 10mS (mostly drivers

 * with CPUFREQ_ETERNAL), this governor will not work.

 * All times here are in uS.

 */

static unsigned int def_sampling_rate;

#define MIN_SAMPLING_RATE_RATIO                 (2)

/* for correct statistics, we need at least 10 ticks between each measure */

#define MIN_STAT_SAMPLING_RATE                  \

                        (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))

#define MIN_SAMPLING_RATE                       \

                        (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)

#define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)

#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)

#define DEF_SAMPLING_DOWN_FACTOR                (1)

#define MAX_SAMPLING_DOWN_FACTOR                (10)

#define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

struct cpu_dbs_info_s {

        struct cpufreq_policy *cur_policy;

        unsigned int prev_cpu_idle_up;

        unsigned int prev_cpu_idle_down;

        unsigned int enable;

        unsigned int down_skip;

        unsigned int requested_freq;

};

static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);

static unsigned int dbs_enable; /* number of CPUs using this policy */

/*

 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug

 * lock and dbs_mutex. cpu_hotplug lock should always be held before

 * dbs_mutex. If any function that can potentially take cpu_hotplug lock

 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then

 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock

 * is recursive for the same process. -Venki

 */

static DEFINE_MUTEX (dbs_mutex);

static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer);

struct dbs_tuners {

        unsigned int sampling_rate;

        unsigned int sampling_down_factor;

        unsigned int up_threshold;

        unsigned int down_threshold;

        unsigned int ignore_nice;

        unsigned int freq_step;

};

static struct dbs_tuners dbs_tuners_ins = {

        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,

        .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,

        .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,

        .ignore_nice = 0,

        .freq_step = 5,

};

static inline unsigned int get_cpu_idle_time(unsigned int cpu)

{

        unsigned int add_nice = 0, ret;

        if (dbs_tuners_ins.ignore_nice)

                add_nice = kstat_cpu(cpu).cpustat.nice;

        ret = kstat_cpu(cpu).cpustat.idle +

                kstat_cpu(cpu).cpustat.iowait +

                add_nice;

        return ret;

}

/* keep track of frequency transitions */

static int

dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

                     void *data)

{

        struct cpufreq_freqs *freq = data;

        struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info,

                                                        freq->cpu);

        if (!this_dbs_info->enable)

                return 0;

        this_dbs_info->requested_freq = freq->new;

        return 0;

}

static struct notifier_block dbs_cpufreq_notifier_block = {

        .notifier_call = dbs_cpufreq_notifier

};

/************************** sysfs interface ************************/

static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)

{

        return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);

}

static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)

{

        return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);

}

#define define_one_ro(_name)                            \

static struct freq_attr _name =                         \

__ATTR(_name, 0444, show_##_name, NULL)

define_one_ro(sampling_rate_max);

define_one_ro(sampling_rate_min);

/* cpufreq_conservative Governor Tunables */

#define show_one(file_name, object)                                     \

static ssize_t show_##file_name                                         \

(struct cpufreq_policy *unused, char *buf)                              \

{                                                                       \

        return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \

}

show_one(sampling_rate, sampling_rate);

show_one(sampling_down_factor, sampling_down_factor);

show_one(up_threshold, up_threshold);

show_one(down_threshold, down_threshold);

show_one(ignore_nice_load, ignore_nice);

show_one(freq_step, freq_step);

static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        ret = sscanf (buf, "%u", &input);

        if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)

                return -EINVAL;

        mutex_lock(&dbs_mutex);

        dbs_tuners_ins.sampling_down_factor = input;

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_sampling_rate(struct cpufreq_policy *unused,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        ret = sscanf (buf, "%u", &input);

        mutex_lock(&dbs_mutex);

        if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {

                mutex_unlock(&dbs_mutex);

                return -EINVAL;

        }

        dbs_tuners_ins.sampling_rate = input;

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_up_threshold(struct cpufreq_policy *unused,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        ret = sscanf (buf, "%u", &input);

        mutex_lock(&dbs_mutex);

        if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {

                mutex_unlock(&dbs_mutex);

                return -EINVAL;

        }

        dbs_tuners_ins.up_threshold = input;

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_down_threshold(struct cpufreq_policy *unused,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        ret = sscanf (buf, "%u", &input);

        mutex_lock(&dbs_mutex);

        if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {

                mutex_unlock(&dbs_mutex);

                return -EINVAL;

        }

        dbs_tuners_ins.down_threshold = input;

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        unsigned int j;

        ret = sscanf(buf, "%u", &input);

        if (ret != 1)

                return -EINVAL;

        if (input > 1)

                input = 1;

        mutex_lock(&dbs_mutex);

        if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */

                mutex_unlock(&dbs_mutex);

                return count;

        }

        dbs_tuners_ins.ignore_nice = input;

        /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */

        for_each_online_cpu(j) {

                struct cpu_dbs_info_s *j_dbs_info;

                j_dbs_info = &per_cpu(cpu_dbs_info, j);

                j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);

                j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;

        }

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_freq_step(struct cpufreq_policy *policy,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

        ret = sscanf(buf, "%u", &input);

        if (ret != 1)

                return -EINVAL;

        if (input > 100)

                input = 100;

        /* no need to test here if freq_step is zero as the user might actually

         * want this, they would be crazy though :) */

        mutex_lock(&dbs_mutex);

        dbs_tuners_ins.freq_step = input;

        mutex_unlock(&dbs_mutex);

        return count;

}

#define define_one_rw(_name) \

static struct freq_attr _name = \

__ATTR(_name, 0644, show_##_name, store_##_name)

define_one_rw(sampling_rate);

define_one_rw(sampling_down_factor);

define_one_rw(up_threshold);

define_one_rw(down_threshold);

define_one_rw(ignore_nice_load);

define_one_rw(freq_step);

static struct attribute * dbs_attributes[] = {

        &sampling_rate_max.attr,

        &sampling_rate_min.attr,

        &sampling_rate.attr,

        &sampling_down_factor.attr,

        &up_threshold.attr,

        &down_threshold.attr,

        &ignore_nice_load.attr,

        &freq_step.attr,

        NULL

};

static struct attribute_group dbs_attr_group = {

        .attrs = dbs_attributes,

        .name = "conservative",

};

/************************** sysfs end ************************/

static void dbs_check_cpu(int cpu)

{

        unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;

        unsigned int tmp_idle_ticks, total_idle_ticks;

        unsigned int freq_step;

        unsigned int freq_down_sampling_rate;

        struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);

        struct cpufreq_policy *policy;

        if (!this_dbs_info->enable)

                return;

        policy = this_dbs_info->cur_policy;

        /*

         * The default safe range is 20% to 80%

         * Every sampling_rate, we check

         *      - If current idle time is less than 20%, then we try to

         *        increase frequency

         * Every sampling_rate*sampling_down_factor, we check

         *      - If current idle time is more than 80%, then we try to

         *        decrease frequency

         *

         * Any frequency increase takes it to the maximum frequency.

         * Frequency reduction happens at minimum steps of

         * 5% (default) of max_frequency

         */

        /* Check for frequency increase */

        idle_ticks = UINT_MAX;

        /* Check for frequency increase */

        total_idle_ticks = get_cpu_idle_time(cpu);

        tmp_idle_ticks = total_idle_ticks -

                this_dbs_info->prev_cpu_idle_up;

        this_dbs_info->prev_cpu_idle_up = total_idle_ticks;

        if (tmp_idle_ticks < idle_ticks)

                idle_ticks = tmp_idle_ticks;

        /* Scale idle ticks by 100 and compare with up and down ticks */

        idle_ticks *= 100;

        up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *

                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

        if (idle_ticks < up_idle_ticks) {

                this_dbs_info->down_skip = 0;

                this_dbs_info->prev_cpu_idle_down =

                        this_dbs_info->prev_cpu_idle_up;

                /* if we are already at full speed then break out early */

                if (this_dbs_info->requested_freq == policy->max)

                        return;

                freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;

                /* max freq cannot be less than 100. But who knows.... */

                if (unlikely(freq_step == 0))

                        freq_step = 5;

                this_dbs_info->requested_freq += freq_step;

                if (this_dbs_info->requested_freq > policy->max)

                        this_dbs_info->requested_freq = policy->max;

                __cpufreq_driver_target(policy, this_dbs_info->requested_freq,

                        CPUFREQ_RELATION_H);

                return;

        }

        /* Check for frequency decrease */

        this_dbs_info->down_skip++;

        if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)

                return;

        /* Check for frequency decrease */

        total_idle_ticks = this_dbs_info->prev_cpu_idle_up;

        tmp_idle_ticks = total_idle_ticks -

                this_dbs_info->prev_cpu_idle_down;

        this_dbs_info->prev_cpu_idle_down = total_idle_ticks;

        if (tmp_idle_ticks < idle_ticks)

                idle_ticks = tmp_idle_ticks;

        /* Scale idle ticks by 100 and compare with up and down ticks */

        idle_ticks *= 100;

        this_dbs_info->down_skip = 0;

        freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *

                dbs_tuners_ins.sampling_down_factor;

        down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *

                usecs_to_jiffies(freq_down_sampling_rate);

        if (idle_ticks > down_idle_ticks) {

                /*

                 * if we are already at the lowest speed then break out early

                 * or if we 'cannot' reduce the speed as the user might want

                 * freq_step to be zero

                 */

                if (this_dbs_info->requested_freq == policy->min

                                || dbs_tuners_ins.freq_step == 0)

                        return;

                freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;

                /* max freq cannot be less than 100. But who knows.... */

                if (unlikely(freq_step == 0))

                        freq_step = 5;

                this_dbs_info->requested_freq -= freq_step;

                if (this_dbs_info->requested_freq < policy->min)

                        this_dbs_info->requested_freq = policy->min;

                __cpufreq_driver_target(policy, this_dbs_info->requested_freq,

                                CPUFREQ_RELATION_H);

                return;

        }

}

static void do_dbs_timer(struct work_struct *work)

{

        int i;

        mutex_lock(&dbs_mutex);

        for_each_online_cpu(i)

                dbs_check_cpu(i);

        schedule_delayed_work(&dbs_work,

                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));

        mutex_unlock(&dbs_mutex);

}

static inline void dbs_timer_init(void)

{

        schedule_delayed_work(&dbs_work,

                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate));

        return;

}

static inline void dbs_timer_exit(void)

{

        cancel_delayed_work(&dbs_work);

        return;

}

static int cpufreq_governor_dbs(struct cpufreq_policy *policy,

                                   unsigned int event)

{

        unsigned int cpu = policy->cpu;

        struct cpu_dbs_info_s *this_dbs_info;

        unsigned int j;

        int rc;

        this_dbs_info = &per_cpu(cpu_dbs_info, cpu);

        switch (event) {

        case CPUFREQ_GOV_START:

                if ((!cpu_online(cpu)) || (!policy->cur))

                        return -EINVAL;

                if (this_dbs_info->enable) /* Already enabled */

                        break;

                mutex_lock(&dbs_mutex);

                rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);

                if (rc) {

                        mutex_unlock(&dbs_mutex);

                        return rc;

                }

                for_each_cpu_mask(j, policy->cpus) {

                        struct cpu_dbs_info_s *j_dbs_info;

                        j_dbs_info = &per_cpu(cpu_dbs_info, j);

                        j_dbs_info->cur_policy = policy;

                        j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);

                        j_dbs_info->prev_cpu_idle_down

                                = j_dbs_info->prev_cpu_idle_up;

                }

                this_dbs_info->enable = 1;

                this_dbs_info->down_skip = 0;

                this_dbs_info->requested_freq = policy->cur;

                dbs_enable++;

                /*

                 * Start the timerschedule work, when this governor

                 * is used for first time

                 */

                if (dbs_enable == 1) {

                        unsigned int latency;

                        /* policy latency is in nS. Convert it to uS first */

                        latency = policy->cpuinfo.transition_latency / 1000;

                        if (latency == 0)

                                latency = 1;

                        def_sampling_rate = 10 * latency *

                                        DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;

                        if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)

                                def_sampling_rate = MIN_STAT_SAMPLING_RATE;

                        dbs_tuners_ins.sampling_rate = def_sampling_rate;

                        dbs_timer_init();

                        cpufreq_register_notifier(

                                        &dbs_cpufreq_notifier_block,

                                        CPUFREQ_TRANSITION_NOTIFIER);

                }

                mutex_unlock(&dbs_mutex);

                break;

        case CPUFREQ_GOV_STOP:

                mutex_lock(&dbs_mutex);

                this_dbs_info->enable = 0;

                sysfs_remove_group(&policy->kobj, &dbs_attr_group);

                dbs_enable--;

                /*

                 * Stop the timerschedule work, when this governor

                 * is used for first time

                 */

                if (dbs_enable == 0) {

                        dbs_timer_exit();

                        cpufreq_unregister_notifier(

                                        &dbs_cpufreq_notifier_block,

                                        CPUFREQ_TRANSITION_NOTIFIER);

                }

                mutex_unlock(&dbs_mutex);

                break;

        case CPUFREQ_GOV_LIMITS:

                mutex_lock(&dbs_mutex);

                if (policy->max < this_dbs_info->cur_policy->cur)

                        __cpufreq_driver_target(

                                        this_dbs_info->cur_policy,

                                        policy->max, CPUFREQ_RELATION_H);

                else if (policy->min > this_dbs_info->cur_policy->cur)

                        __cpufreq_driver_target(

                                        this_dbs_info->cur_policy,

                                        policy->min, CPUFREQ_RELATION_L);

                mutex_unlock(&dbs_mutex);

                break;

        }

        return 0;

}

struct cpufreq_governor cpufreq_gov_conservative = {

        .name                   = "conservative",

        .governor               = cpufreq_governor_dbs,

        .max_transition_latency = TRANSITION_LATENCY_LIMIT,

        .owner                  = THIS_MODULE,

};

EXPORT_SYMBOL(cpufreq_gov_conservative);

static int __init cpufreq_gov_dbs_init(void)

{

        return cpufreq_register_governor(&cpufreq_gov_conservative);

}

static void __exit cpufreq_gov_dbs_exit(void)

{

        /* Make sure that the scheduled work is indeed not running */

        flush_scheduled_work();

        cpufreq_unregister_governor(&cpufreq_gov_conservative);

}

MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");

MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "

                "Low Latency Frequency Transition capable processors "

                "optimised for use in a battery environment");

MODULE_LICENSE ("GPL");

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE

fs_initcall(cpufreq_gov_dbs_init);

#else

module_init(cpufreq_gov_dbs_init);

#endif

module_exit(cpufreq_gov_dbs_exit);