/*
 *  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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/kobject.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/percpu-defs.h>
#include <linux/sysfs.h>
#include <linux/tick.h>
#include <linux/types.h>

#include "cpufreq_governor.h"

/* On-demand governor macros */
#define DEF_FREQUENCY_DOWN_DIFFERENTIAL         (10)
#define DEF_FREQUENCY_UP_THRESHOLD              (80)
#define DEF_SAMPLING_DOWN_FACTOR                (1)
#define MAX_SAMPLING_DOWN_FACTOR                (100000)
#define MICRO_FREQUENCY_DOWN_DIFFERENTIAL       (3)
#define MICRO_FREQUENCY_UP_THRESHOLD            (95)
#define MICRO_FREQUENCY_MIN_SAMPLE_RATE         (10000)
#define MIN_FREQUENCY_UP_THRESHOLD              (11)
#define MAX_FREQUENCY_UP_THRESHOLD              (100)

static struct dbs_data od_dbs_data;
static DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
static struct cpufreq_governor cpufreq_gov_ondemand;
#endif

static struct od_dbs_tuners od_tuners = {
        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
        .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
        .adj_up_threshold = DEF_FREQUENCY_UP_THRESHOLD -
                            DEF_FREQUENCY_DOWN_DIFFERENTIAL,
        .ignore_nice = 0,
        .powersave_bias = 0,
};

static void ondemand_powersave_bias_init_cpu(int cpu)
{
        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);

        dbs_info->freq_table = cpufreq_frequency_get_table(cpu);
        dbs_info->freq_lo = 0;
}

/*
 * Not all CPUs want IO time to be accounted as busy; this depends on how
 * efficient idling at a higher frequency/voltage is.
 * Pavel Machek says this is not so for various generations of AMD and old
 * Intel systems.
 * Mike Chan (android.com) claims this is also not true for ARM.
 * Because of this, whitelist specific known (series) of CPUs by default, and
 * leave all others up to the user.
 */
static int should_io_be_busy(void)
{
#if defined(CONFIG_X86)
        /*
         * For Intel, Core 2 (model 15) and later have an efficient idle.
         */
        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
                        boot_cpu_data.x86 == 6 &&
                        boot_cpu_data.x86_model >= 15)
                return 1;
#endif
        return 0;
}

/*
 * 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 od_cpu_dbs_info_s *dbs_info = &per_cpu(od_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 * od_tuners.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(od_tuners.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) {
                ondemand_powersave_bias_init_cpu(i);
        }
}

static void dbs_freq_increase(struct cpufreq_policy *p, unsigned int freq)
{
        if (od_tuners.powersave_bias)
                freq = powersave_bias_target(p, freq, CPUFREQ_RELATION_H);
        else if (p->cur == p->max)
                return;

        __cpufreq_driver_target(p, freq, od_tuners.powersave_bias ?
                        CPUFREQ_RELATION_L : CPUFREQ_RELATION_H);
}

/*
 * 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 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
 */
static void od_check_cpu(int cpu, unsigned int load_freq)
{
        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
        struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;

        dbs_info->freq_lo = 0;

        /* Check for frequency increase */
        if (load_freq > od_tuners.up_threshold * policy->cur) {
                /* If switching to max speed, apply sampling_down_factor */
                if (policy->cur < policy->max)
                        dbs_info->rate_mult =
                                od_tuners.sampling_down_factor;
                dbs_freq_increase(policy, policy->max);
                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_freq < od_tuners.adj_up_threshold * policy->cur) {
                unsigned int freq_next;
                freq_next = load_freq / od_tuners.adj_up_threshold;

                /* No longer fully busy, reset rate_mult */
                dbs_info->rate_mult = 1;

                if (freq_next < policy->min)
                        freq_next = policy->min;

                if (!od_tuners.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 od_dbs_timer(struct work_struct *work)
{
        struct delayed_work *dw = to_delayed_work(work);
        struct od_cpu_dbs_info_s *dbs_info =
                container_of(work, struct od_cpu_dbs_info_s, cdbs.work.work);
        unsigned int cpu = dbs_info->cdbs.cur_policy->cpu;
        struct od_cpu_dbs_info_s *core_dbs_info = &per_cpu(od_cpu_dbs_info,
                        cpu);
        int delay, sample_type = core_dbs_info->sample_type;
        bool eval_load;

        mutex_lock(&core_dbs_info->cdbs.timer_mutex);
        eval_load = need_load_eval(&core_dbs_info->cdbs,
                        od_tuners.sampling_rate);

        /* Common NORMAL_SAMPLE setup */
        core_dbs_info->sample_type = OD_NORMAL_SAMPLE;
        if (sample_type == OD_SUB_SAMPLE) {
                delay = core_dbs_info->freq_lo_jiffies;
                if (eval_load)
                        __cpufreq_driver_target(core_dbs_info->cdbs.cur_policy,
                                                core_dbs_info->freq_lo,
                                                CPUFREQ_RELATION_H);
        } else {
                if (eval_load)
                        dbs_check_cpu(&od_dbs_data, cpu);
                if (core_dbs_info->freq_lo) {
                        /* Setup timer for SUB_SAMPLE */
                        core_dbs_info->sample_type = OD_SUB_SAMPLE;
                        delay = core_dbs_info->freq_hi_jiffies;
                } else {
                        delay = delay_for_sampling_rate(od_tuners.sampling_rate
                                                * core_dbs_info->rate_mult);
                }
        }

        schedule_delayed_work_on(smp_processor_id(), dw, delay);
        mutex_unlock(&core_dbs_info->cdbs.timer_mutex);
}

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

static ssize_t show_sampling_rate_min(struct kobject *kobj,
                                      struct attribute *attr, char *buf)
{
        return sprintf(buf, "%u\n", od_dbs_data.min_sampling_rate);
}

/**
 * update_sampling_rate - update sampling rate effective immediately if needed.
 * @new_rate: new sampling rate
 *
 * If new rate is smaller than the old, simply updating
 * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the
 * original sampling_rate was 1 second and the requested new sampling rate is 10
 * ms because the user needs immediate reaction from ondemand governor, but not
 * sure if higher frequency will be required or not, then, the governor may
 * change the sampling rate too late; up to 1 second later. Thus, if we are
 * reducing the sampling rate, we need to make the new value effective
 * immediately.
 */
static void update_sampling_rate(unsigned int new_rate)
{
        int cpu;

        od_tuners.sampling_rate = new_rate = max(new_rate,
                        od_dbs_data.min_sampling_rate);

        for_each_online_cpu(cpu) {
                struct cpufreq_policy *policy;
                struct od_cpu_dbs_info_s *dbs_info;
                unsigned long next_sampling, appointed_at;

                policy = cpufreq_cpu_get(cpu);
                if (!policy)
                        continue;
                if (policy->governor != &cpufreq_gov_ondemand) {
                        cpufreq_cpu_put(policy);
                        continue;
                }
                dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
                cpufreq_cpu_put(policy);

                mutex_lock(&dbs_info->cdbs.timer_mutex);

                if (!delayed_work_pending(&dbs_info->cdbs.work)) {
                        mutex_unlock(&dbs_info->cdbs.timer_mutex);
                        continue;
                }

                next_sampling = jiffies + usecs_to_jiffies(new_rate);
                appointed_at = dbs_info->cdbs.work.timer.expires;

                if (time_before(next_sampling, appointed_at)) {

                        mutex_unlock(&dbs_info->cdbs.timer_mutex);
                        cancel_delayed_work_sync(&dbs_info->cdbs.work);
                        mutex_lock(&dbs_info->cdbs.timer_mutex);

                        schedule_delayed_work_on(cpu, &dbs_info->cdbs.work,
                                        usecs_to_jiffies(new_rate));

                }
                mutex_unlock(&dbs_info->cdbs.timer_mutex);
        }
}

static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
                                   const char *buf, size_t count)
{
        unsigned int input;
        int ret;
        ret = sscanf(buf, "%u", &input);
        if (ret != 1)
                return -EINVAL;
        update_sampling_rate(input);
        return count;
}

static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
                                   const char *buf, size_t count)
{
        unsigned int input;
        int ret;

        ret = sscanf(buf, "%u", &input);
        if (ret != 1)
                return -EINVAL;
        od_tuners.io_is_busy = !!input;
        return count;
}

static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
                                  const char *buf, size_t count)
{
        unsigned int input;
        int ret;
        ret = sscanf(buf, "%u", &input);

        if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
                        input < MIN_FREQUENCY_UP_THRESHOLD) {
                return -EINVAL;
        }
        /* Calculate the new adj_up_threshold */
        od_tuners.adj_up_threshold += input;
        od_tuners.adj_up_threshold -= od_tuners.up_threshold;

        od_tuners.up_threshold = input;
        return count;
}

static ssize_t store_sampling_down_factor(struct kobject *a,
                        struct attribute *b, const char *buf, size_t count)
{
        unsigned int input, j;
        int ret;
        ret = sscanf(buf, "%u", &input);

        if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
                return -EINVAL;
        od_tuners.sampling_down_factor = input;

        /* Reset down sampling multiplier in case it was active */
        for_each_online_cpu(j) {
                struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
                                j);
                dbs_info->rate_mult = 1;
        }
        return count;
}

static ssize_t store_ignore_nice_load(struct kobject *a, struct attribute *b,
                                      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;

        if (input == od_tuners.ignore_nice) { /* nothing to do */
                return count;
        }
        od_tuners.ignore_nice = input;

        /* we need to re-evaluate prev_cpu_idle */
        for_each_online_cpu(j) {
                struct od_cpu_dbs_info_s *dbs_info;
                dbs_info = &per_cpu(od_cpu_dbs_info, j);
                dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
                                                &dbs_info->cdbs.prev_cpu_wall);
                if (od_tuners.ignore_nice)
                        dbs_info->cdbs.prev_cpu_nice =
                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];

        }
        return count;
}

static ssize_t store_powersave_bias(struct kobject *a, struct attribute *b,
                                    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;

        od_tuners.powersave_bias = input;
        ondemand_powersave_bias_init();
        return count;
}

show_one(od, sampling_rate, sampling_rate);
show_one(od, io_is_busy, io_is_busy);
show_one(od, up_threshold, up_threshold);
show_one(od, sampling_down_factor, sampling_down_factor);
show_one(od, ignore_nice_load, ignore_nice);
show_one(od, powersave_bias, powersave_bias);

define_one_global_rw(sampling_rate);
define_one_global_rw(io_is_busy);
define_one_global_rw(up_threshold);
define_one_global_rw(sampling_down_factor);
define_one_global_rw(ignore_nice_load);
define_one_global_rw(powersave_bias);
define_one_global_ro(sampling_rate_min);

static struct attribute *dbs_attributes[] = {
        &sampling_rate_min.attr,
        &sampling_rate.attr,
        &up_threshold.attr,
        &sampling_down_factor.attr,
        &ignore_nice_load.attr,
        &powersave_bias.attr,
        &io_is_busy.attr,
        NULL
};

static struct attribute_group od_attr_group = {
        .attrs = dbs_attributes,
        .name = "ondemand",
};

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

define_get_cpu_dbs_routines(od_cpu_dbs_info);

static struct od_ops od_ops = {
        .io_busy = should_io_be_busy,
        .powersave_bias_init_cpu = ondemand_powersave_bias_init_cpu,
        .powersave_bias_target = powersave_bias_target,
        .freq_increase = dbs_freq_increase,
};

static struct dbs_data od_dbs_data = {
        .governor = GOV_ONDEMAND,
        .attr_group = &od_attr_group,
        .tuners = &od_tuners,
        .get_cpu_cdbs = get_cpu_cdbs,
        .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
        .gov_dbs_timer = od_dbs_timer,
        .gov_check_cpu = od_check_cpu,
        .gov_ops = &od_ops,
};

static int od_cpufreq_governor_dbs(struct cpufreq_policy *policy,
                unsigned int event)
{
        return cpufreq_governor_dbs(&od_dbs_data, policy, event);
}

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
static
#endif
struct cpufreq_governor cpufreq_gov_ondemand = {
        .name                   = "ondemand",
        .governor               = od_cpufreq_governor_dbs,
        .max_transition_latency = TRANSITION_LATENCY_LIMIT,
        .owner                  = THIS_MODULE,
};

static int __init cpufreq_gov_dbs_init(void)
{
        u64 idle_time;
        int cpu = get_cpu();

        mutex_init(&od_dbs_data.mutex);
        idle_time = get_cpu_idle_time_us(cpu, NULL);
        put_cpu();
        if (idle_time != -1ULL) {
                /* Idle micro accounting is supported. Use finer thresholds */
                od_tuners.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
                od_tuners.adj_up_threshold = MICRO_FREQUENCY_UP_THRESHOLD -
                                             MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
                /*
                 * In nohz/micro accounting case we set the minimum frequency
                 * not depending on HZ, but fixed (very low). The deferred
                 * timer might skip some samples if idle/sleeping as needed.
                */
                od_dbs_data.min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
        } else {
                /* For correct statistics, we need 10 ticks for each measure */
                od_dbs_data.min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
                        jiffies_to_usecs(10);
        }

        return cpufreq_register_governor(&cpufreq_gov_ondemand);
}

static void __exit cpufreq_gov_dbs_exit(void)
{
        cpufreq_unregister_governor(&cpufreq_gov_ondemand);
}

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);