/*
 *  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/cpu.h>
#include <linux/percpu-defs.h>
#include <linux/slab.h>
#include <linux/tick.h>
#include "cpufreq_governor.h"

/* On-demand governor macros */
#define DEF_FREQUENCY_UP_THRESHOLD              (80)
#define DEF_SAMPLING_DOWN_FACTOR                (1)
#define MAX_SAMPLING_DOWN_FACTOR                (100000)
#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 DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);

static struct od_ops od_ops;

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
static struct cpufreq_governor cpufreq_gov_ondemand;
#endif

static unsigned int default_powersave_bias;

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 generic_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);
        struct dbs_data *dbs_data = policy->governor_data;
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;

        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 *policy, unsigned int freq)
{
        struct dbs_data *dbs_data = policy->governor_data;
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;

        if (od_tuners->powersave_bias)
                freq = od_ops.powersave_bias_target(policy, freq,
                                CPUFREQ_RELATION_H);
        else if (policy->cur == policy->max)
                return;

        __cpufreq_driver_target(policy, 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. Else, we adjust the frequency
 * proportional to load.
 */
static void od_check_cpu(int cpu, unsigned int load)
{
        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info, cpu);
        struct cpufreq_policy *policy = dbs_info->cdbs.shared->policy;
        struct dbs_data *dbs_data = policy->governor_data;
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;

        dbs_info->freq_lo = 0;

        /* Check for frequency increase */
        if (load > od_tuners->up_threshold) {
                /* 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);
        } else {
                /* Calculate the next frequency proportional to load */
                unsigned int freq_next, min_f, max_f;

                min_f = policy->cpuinfo.min_freq;
                max_f = policy->cpuinfo.max_freq;
                freq_next = min_f + load * (max_f - min_f) / 100;

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

                if (!od_tuners->powersave_bias) {
                        __cpufreq_driver_target(policy, freq_next,
                                        CPUFREQ_RELATION_C);
                        return;
                }

                freq_next = od_ops.powersave_bias_target(policy, freq_next,
                                        CPUFREQ_RELATION_L);
                __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_C);
        }
}

static unsigned int od_dbs_timer(struct cpu_dbs_info *cdbs,
                                 struct dbs_data *dbs_data, bool modify_all)
{
        struct cpufreq_policy *policy = cdbs->shared->policy;
        unsigned int cpu = policy->cpu;
        struct od_cpu_dbs_info_s *dbs_info = &per_cpu(od_cpu_dbs_info,
                        cpu);
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        int delay = 0, sample_type = dbs_info->sample_type;

        if (!modify_all)
                goto max_delay;

        /* Common NORMAL_SAMPLE setup */
        dbs_info->sample_type = OD_NORMAL_SAMPLE;
        if (sample_type == OD_SUB_SAMPLE) {
                delay = dbs_info->freq_lo_jiffies;
                __cpufreq_driver_target(policy, dbs_info->freq_lo,
                                        CPUFREQ_RELATION_H);
        } else {
                dbs_check_cpu(dbs_data, cpu);
                if (dbs_info->freq_lo) {
                        /* Setup timer for SUB_SAMPLE */
                        dbs_info->sample_type = OD_SUB_SAMPLE;
                        delay = dbs_info->freq_hi_jiffies;
                }
        }

max_delay:
        if (!delay)
                delay = delay_for_sampling_rate(od_tuners->sampling_rate
                                * dbs_info->rate_mult);

        return delay;
}

/************************** sysfs interface ************************/
static struct common_dbs_data od_dbs_cdata;

/**
 * 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(struct dbs_data *dbs_data,
                unsigned int new_rate)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        int cpu;

        od_tuners->sampling_rate = new_rate = max(new_rate,
                        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.shared->timer_mutex);

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

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

                if (time_before(next_sampling, appointed_at)) {

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

                        gov_queue_work(dbs_data, policy,
                                       usecs_to_jiffies(new_rate), true);

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

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

        update_sampling_rate(dbs_data, input);
        return count;
}

static ssize_t store_io_is_busy(struct dbs_data *dbs_data, const char *buf,
                size_t count)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        unsigned int input;
        int ret;
        unsigned int j;

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

        /* we need to re-evaluate prev_cpu_idle */
        for_each_online_cpu(j) {
                struct od_cpu_dbs_info_s *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, od_tuners->io_is_busy);
        }
        return count;
}

static ssize_t store_up_threshold(struct dbs_data *dbs_data, const char *buf,
                size_t count)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        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;
        }

        od_tuners->up_threshold = input;
        return count;
}

static ssize_t store_sampling_down_factor(struct dbs_data *dbs_data,
                const char *buf, size_t count)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        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 dbs_data *dbs_data,
                const char *buf, size_t count)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        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_load) { /* nothing to do */
                return count;
        }
        od_tuners->ignore_nice_load = 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, od_tuners->io_is_busy);
                if (od_tuners->ignore_nice_load)
                        dbs_info->cdbs.prev_cpu_nice =
                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];

        }
        return count;
}

static ssize_t store_powersave_bias(struct dbs_data *dbs_data, const char *buf,
                size_t count)
{
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        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_store_one(od, sampling_rate);
show_store_one(od, io_is_busy);
show_store_one(od, up_threshold);
show_store_one(od, sampling_down_factor);
show_store_one(od, ignore_nice_load);
show_store_one(od, powersave_bias);
declare_show_sampling_rate_min(od);

gov_sys_pol_attr_rw(sampling_rate);
gov_sys_pol_attr_rw(io_is_busy);
gov_sys_pol_attr_rw(up_threshold);
gov_sys_pol_attr_rw(sampling_down_factor);
gov_sys_pol_attr_rw(ignore_nice_load);
gov_sys_pol_attr_rw(powersave_bias);
gov_sys_pol_attr_ro(sampling_rate_min);

static struct attribute *dbs_attributes_gov_sys[] = {
        &sampling_rate_min_gov_sys.attr,
        &sampling_rate_gov_sys.attr,
        &up_threshold_gov_sys.attr,
        &sampling_down_factor_gov_sys.attr,
        &ignore_nice_load_gov_sys.attr,
        &powersave_bias_gov_sys.attr,
        &io_is_busy_gov_sys.attr,
        NULL
};

static struct attribute_group od_attr_group_gov_sys = {
        .attrs = dbs_attributes_gov_sys,
        .name = "ondemand",
};

static struct attribute *dbs_attributes_gov_pol[] = {
        &sampling_rate_min_gov_pol.attr,
        &sampling_rate_gov_pol.attr,
        &up_threshold_gov_pol.attr,
        &sampling_down_factor_gov_pol.attr,
        &ignore_nice_load_gov_pol.attr,
        &powersave_bias_gov_pol.attr,
        &io_is_busy_gov_pol.attr,
        NULL
};

static struct attribute_group od_attr_group_gov_pol = {
        .attrs = dbs_attributes_gov_pol,
        .name = "ondemand",
};

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

static int od_init(struct dbs_data *dbs_data, bool notify)
{
        struct od_dbs_tuners *tuners;
        u64 idle_time;
        int cpu;

        tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
        if (!tuners) {
                pr_err("%s: kzalloc failed\n", __func__);
                return -ENOMEM;
        }

        cpu = get_cpu();
        idle_time = get_cpu_idle_time_us(cpu, NULL);
        put_cpu();
        if (idle_time != -1ULL) {
                /* Idle micro accounting is supported. Use finer thresholds */
                tuners->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
                /*
                 * 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.
                */
                dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
        } else {
                tuners->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;

                /* For correct statistics, we need 10 ticks for each measure */
                dbs_data->min_sampling_rate = MIN_SAMPLING_RATE_RATIO *
                        jiffies_to_usecs(10);
        }

        tuners->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
        tuners->ignore_nice_load = 0;
        tuners->powersave_bias = default_powersave_bias;
        tuners->io_is_busy = should_io_be_busy();

        dbs_data->tuners = tuners;
        return 0;
}

static void od_exit(struct dbs_data *dbs_data, bool notify)
{
        kfree(dbs_data->tuners);
}

define_get_cpu_dbs_routines(od_cpu_dbs_info);

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

static struct common_dbs_data od_dbs_cdata = {
        .governor = GOV_ONDEMAND,
        .attr_group_gov_sys = &od_attr_group_gov_sys,
        .attr_group_gov_pol = &od_attr_group_gov_pol,
        .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,
        .init = od_init,
        .exit = od_exit,
        .mutex = __MUTEX_INITIALIZER(od_dbs_cdata.mutex),
};

static void od_set_powersave_bias(unsigned int powersave_bias)
{
        struct cpufreq_policy *policy;
        struct dbs_data *dbs_data;
        struct od_dbs_tuners *od_tuners;
        unsigned int cpu;
        cpumask_t done;

        default_powersave_bias = powersave_bias;
        cpumask_clear(&done);

        get_online_cpus();
        for_each_online_cpu(cpu) {
                struct cpu_common_dbs_info *shared;

                if (cpumask_test_cpu(cpu, &done))
                        continue;

                shared = per_cpu(od_cpu_dbs_info, cpu).cdbs.shared;
                if (!shared)
                        continue;

                policy = shared->policy;
                cpumask_or(&done, &done, policy->cpus);

                if (policy->governor != &cpufreq_gov_ondemand)
                        continue;

                dbs_data = policy->governor_data;
                od_tuners = dbs_data->tuners;
                od_tuners->powersave_bias = default_powersave_bias;
        }
        put_online_cpus();
}

void od_register_powersave_bias_handler(unsigned int (*f)
                (struct cpufreq_policy *, unsigned int, unsigned int),
                unsigned int powersave_bias)
{
        od_ops.powersave_bias_target = f;
        od_set_powersave_bias(powersave_bias);
}
EXPORT_SYMBOL_GPL(od_register_powersave_bias_handler);

void od_unregister_powersave_bias_handler(void)
{
        od_ops.powersave_bias_target = generic_powersave_bias_target;
        od_set_powersave_bias(0);
}
EXPORT_SYMBOL_GPL(od_unregister_powersave_bias_handler);

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