/*
 *  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);