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/*

 *  drivers/cpufreq/cpufreq_ondemand.c

 *

 *  Copyright (C)  2001 Russell King

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

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

 *

 * 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/init.h>

#include <linux/cpufreq.h>

#include <linux/cpu.h>

#include <linux/jiffies.h>

#include <linux/kernel_stat.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 MIN_FREQUENCY_UP_THRESHOLD              (11)

#define MAX_FREQUENCY_UP_THRESHOLD              (100)

/*

 * 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 TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

/* Sampling types */

enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};

struct cpu_dbs_info_s {

        cputime64_t prev_cpu_idle;

        cputime64_t prev_cpu_wall;

        struct cpufreq_policy *cur_policy;

        struct delayed_work work;

        struct cpufreq_frequency_table *freq_table;

        unsigned int freq_lo;

        unsigned int freq_lo_jiffies;

        unsigned int freq_hi_jiffies;

        int cpu;

        unsigned int enable:1,

                     sample_type:1;

};

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 struct workqueue_struct  *kondemand_wq;

static struct dbs_tuners {

        unsigned int sampling_rate;

        unsigned int up_threshold;

        unsigned int ignore_nice;

        unsigned int powersave_bias;

} dbs_tuners_ins = {

        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,

        .ignore_nice = 0,

        .powersave_bias = 0,

};

static inline cputime64_t get_cpu_idle_time(unsigned int cpu)

{

        cputime64_t idle_time;

        cputime64_t cur_jiffies;

        cputime64_t busy_time;

        cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());

        busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user,

                        kstat_cpu(cpu).cpustat.system);

        busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq);

        busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq);

        busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal);

        if (!dbs_tuners_ins.ignore_nice) {

                busy_time = cputime64_add(busy_time,

                                kstat_cpu(cpu).cpustat.nice);

        }

        idle_time = cputime64_sub(cur_jiffies, busy_time);

        return idle_time;

}

/*

 * Find right freq to be set now with powersave_bias on.

 * Returns the freq_hi to be used right now and will set freq_hi_jiffies,

 * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.

 */

static unsigned int powersave_bias_target(struct cpufreq_policy *policy,

                                          unsigned int freq_next,

                                          unsigned int relation)

{

        unsigned int freq_req, freq_reduc, freq_avg;

        unsigned int freq_hi, freq_lo;

        unsigned int index = 0;

        unsigned int jiffies_total, jiffies_hi, jiffies_lo;

        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);

        if (!dbs_info->freq_table) {

                dbs_info->freq_lo = 0;

                dbs_info->freq_lo_jiffies = 0;

                return freq_next;

        }

        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,

                        relation, &index);

        freq_req = dbs_info->freq_table[index].frequency;

        freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;

        freq_avg = freq_req - freq_reduc;

        /* Find freq bounds for freq_avg in freq_table */

        index = 0;

        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,

                        CPUFREQ_RELATION_H, &index);

        freq_lo = dbs_info->freq_table[index].frequency;

        index = 0;

        cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,

                        CPUFREQ_RELATION_L, &index);

        freq_hi = dbs_info->freq_table[index].frequency;

        /* Find out how long we have to be in hi and lo freqs */

        if (freq_hi == freq_lo) {

                dbs_info->freq_lo = 0;

                dbs_info->freq_lo_jiffies = 0;

                return freq_lo;

        }

        jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

        jiffies_hi = (freq_avg - freq_lo) * jiffies_total;

        jiffies_hi += ((freq_hi - freq_lo) / 2);

        jiffies_hi /= (freq_hi - freq_lo);

        jiffies_lo = jiffies_total - jiffies_hi;

        dbs_info->freq_lo = freq_lo;

        dbs_info->freq_lo_jiffies = jiffies_lo;

        dbs_info->freq_hi_jiffies = jiffies_hi;

        return freq_hi;

}

static void ondemand_powersave_bias_init(void)

{

        int i;

        for_each_online_cpu(i) {

                struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);

                dbs_info->freq_table = cpufreq_frequency_get_table(i);

                dbs_info->freq_lo = 0;

        }

}

/************************** 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_ondemand 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(up_threshold, up_threshold);

show_one(ignore_nice_load, ignore_nice);

show_one(powersave_bias, powersave_bias);

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 > MAX_FREQUENCY_UP_THRESHOLD ||

                        input < MIN_FREQUENCY_UP_THRESHOLD) {

                mutex_unlock(&dbs_mutex);

                return -EINVAL;

        }

        dbs_tuners_ins.up_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 */

        for_each_online_cpu(j) {

                struct cpu_dbs_info_s *dbs_info;

                dbs_info = &per_cpu(cpu_dbs_info, j);

                dbs_info->prev_cpu_idle = get_cpu_idle_time(j);

                dbs_info->prev_cpu_wall = get_jiffies_64();

        }

        mutex_unlock(&dbs_mutex);

        return count;

}

static ssize_t store_powersave_bias(struct cpufreq_policy *unused,

                const char *buf, size_t count)

{

        unsigned int input;

        int ret;

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

        if (ret != 1)

                return -EINVAL;

        if (input > 1000)

                input = 1000;

        mutex_lock(&dbs_mutex);

        dbs_tuners_ins.powersave_bias = input;

        ondemand_powersave_bias_init();

        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(up_threshold);

define_one_rw(ignore_nice_load);

define_one_rw(powersave_bias);

static struct attribute * dbs_attributes[] = {

        &sampling_rate_max.attr,

        &sampling_rate_min.attr,

        &sampling_rate.attr,

        &up_threshold.attr,

        &ignore_nice_load.attr,

        &powersave_bias.attr,

        NULL

};

static struct attribute_group dbs_attr_group = {

        .attrs = dbs_attributes,

        .name = "ondemand",

};

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

static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)

{

        unsigned int idle_ticks, total_ticks;

        unsigned int load = 0;

        cputime64_t cur_jiffies;

        struct cpufreq_policy *policy;

        unsigned int j;

        if (!this_dbs_info->enable)

                return;

        this_dbs_info->freq_lo = 0;

        policy = this_dbs_info->cur_policy;

        cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());

        total_ticks = (unsigned int) cputime64_sub(cur_jiffies,

                        this_dbs_info->prev_cpu_wall);

        this_dbs_info->prev_cpu_wall = get_jiffies_64();

        if (!total_ticks)

                return;

        /*

         * Every sampling_rate, we check, if current idle time is less

         * than 20% (default), then we try to increase frequency

         * Every sampling_rate, we look for a the lowest

         * frequency which can sustain the load while keeping idle time over

         * 30%. If such a frequency exist, we try to decrease to this frequency.

         *

         * Any frequency increase takes it to the maximum frequency.

         * Frequency reduction happens at minimum steps of

         * 5% (default) of current frequency

         */

        /* Get Idle Time */

        idle_ticks = UINT_MAX;

        for_each_cpu_mask(j, policy->cpus) {

                cputime64_t total_idle_ticks;

                unsigned int tmp_idle_ticks;

                struct cpu_dbs_info_s *j_dbs_info;

                j_dbs_info = &per_cpu(cpu_dbs_info, j);

                total_idle_ticks = get_cpu_idle_time(j);

                tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,

                                j_dbs_info->prev_cpu_idle);

                j_dbs_info->prev_cpu_idle = total_idle_ticks;

                if (tmp_idle_ticks < idle_ticks)

                        idle_ticks = tmp_idle_ticks;

        }

        if (likely(total_ticks > idle_ticks))

                load = (100 * (total_ticks - idle_ticks)) / total_ticks;

        /* Check for frequency increase */

        if (load > dbs_tuners_ins.up_threshold) {

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

                if (!dbs_tuners_ins.powersave_bias) {

                        if (policy->cur == policy->max)

                                return;

                        __cpufreq_driver_target(policy, policy->max,

                                CPUFREQ_RELATION_H);

                } else {

                        int freq = powersave_bias_target(policy, policy->max,

                                        CPUFREQ_RELATION_H);

                        __cpufreq_driver_target(policy, freq,

                                CPUFREQ_RELATION_L);

                }

                return;

        }

        /* Check for frequency decrease */

        /* if we cannot reduce the frequency anymore, break out early */

        if (policy->cur == policy->min)

                return;

        /*

         * The optimal frequency is the frequency that is the lowest that

         * can support the current CPU usage without triggering the up

         * policy. To be safe, we focus 10 points under the threshold.

         */

        if (load < (dbs_tuners_ins.up_threshold - 10)) {

                unsigned int freq_next, freq_cur;

                freq_cur = __cpufreq_driver_getavg(policy);

                if (!freq_cur)

                        freq_cur = policy->cur;

                freq_next = (freq_cur * load) /

                        (dbs_tuners_ins.up_threshold - 10);

                if (!dbs_tuners_ins.powersave_bias) {

                        __cpufreq_driver_target(policy, freq_next,

                                        CPUFREQ_RELATION_L);

                } else {

                        int freq = powersave_bias_target(policy, freq_next,

                                        CPUFREQ_RELATION_L);

                        __cpufreq_driver_target(policy, freq,

                                CPUFREQ_RELATION_L);

                }

        }

}

static void do_dbs_timer(struct work_struct *work)

{

        struct cpu_dbs_info_s *dbs_info =

                container_of(work, struct cpu_dbs_info_s, work.work);

        unsigned int cpu = dbs_info->cpu;

        int sample_type = dbs_info->sample_type;

        /* We want all CPUs to do sampling nearly on same jiffy */

        int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

        delay -= jiffies % delay;

        if (lock_policy_rwsem_write(cpu) < 0)

                return;

        if (!dbs_info->enable) {

                unlock_policy_rwsem_write(cpu);

                return;

        }

        /* Common NORMAL_SAMPLE setup */

        dbs_info->sample_type = DBS_NORMAL_SAMPLE;

        if (!dbs_tuners_ins.powersave_bias ||

            sample_type == DBS_NORMAL_SAMPLE) {

                dbs_check_cpu(dbs_info);

                if (dbs_info->freq_lo) {

                        /* Setup timer for SUB_SAMPLE */

                        dbs_info->sample_type = DBS_SUB_SAMPLE;

                        delay = dbs_info->freq_hi_jiffies;

                }

        } else {

                __cpufreq_driver_target(dbs_info->cur_policy,

                                        dbs_info->freq_lo,

                                        CPUFREQ_RELATION_H);

        }

        queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);

        unlock_policy_rwsem_write(cpu);

}

static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)

{

        /* We want all CPUs to do sampling nearly on same jiffy */

        int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

        delay -= jiffies % delay;

        dbs_info->enable = 1;

        ondemand_powersave_bias_init();

        dbs_info->sample_type = DBS_NORMAL_SAMPLE;

        INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);

        queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,

                              delay);

}

static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)

{

        dbs_info->enable = 0;

        cancel_delayed_work(&dbs_info->work);

}

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);

                dbs_enable++;

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

                if (rc) {

                        dbs_enable--;

                        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 = get_cpu_idle_time(j);

                        j_dbs_info->prev_cpu_wall = get_jiffies_64();

                }

                this_dbs_info->cpu = cpu;

                /*

                 * 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 = 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(this_dbs_info);

                mutex_unlock(&dbs_mutex);

                break;

        case CPUFREQ_GOV_STOP:

                mutex_lock(&dbs_mutex);

                dbs_timer_exit(this_dbs_info);

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

                dbs_enable--;

                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_ondemand = {

        .name                   = "ondemand",

        .governor               = cpufreq_governor_dbs,

        .max_transition_latency = TRANSITION_LATENCY_LIMIT,

        .owner                  = THIS_MODULE,

};

EXPORT_SYMBOL(cpufreq_gov_ondemand);

static int __init cpufreq_gov_dbs_init(void)

{

        kondemand_wq = create_workqueue("kondemand");

        if (!kondemand_wq) {

                printk(KERN_ERR "Creation of kondemand failed\n");

                return -EFAULT;

        }

        return cpufreq_register_governor(&cpufreq_gov_ondemand);

}

static void __exit cpufreq_gov_dbs_exit(void)

{

        cpufreq_unregister_governor(&cpufreq_gov_ondemand);

        destroy_workqueue(kondemand_wq);

}

MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");

MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");

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

                   "Low Latency Frequency Transition capable processors");

MODULE_LICENSE("GPL");

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND

fs_initcall(cpufreq_gov_dbs_init);

#else

module_init(cpufreq_gov_dbs_init);

#endif

module_exit(cpufreq_gov_dbs_exit);