/*
 *  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 <linux/sched/cpufreq.h>

#include "cpufreq_ondemand.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              (1)
#define MAX_FREQUENCY_UP_THRESHOLD              (100)

static struct od_ops od_ops;

static unsigned int default_powersave_bias;

/*
 * 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_delay_us,
 * freq_lo, and freq_lo_delay_us 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;
        unsigned int delay_hi_us;
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct od_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
        struct dbs_data *dbs_data = policy_dbs->dbs_data;
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        struct cpufreq_frequency_table *freq_table = policy->freq_table;

        if (!freq_table) {
                dbs_info->freq_lo = 0;
                dbs_info->freq_lo_delay_us = 0;
                return freq_next;
        }

        index = cpufreq_frequency_table_target(policy, freq_next, relation);
        freq_req = 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 = cpufreq_table_find_index_h(policy, freq_avg);
        freq_lo = freq_table[index].frequency;
        index = cpufreq_table_find_index_l(policy, freq_avg);
        freq_hi = 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_delay_us = 0;
                return freq_lo;
        }
        delay_hi_us = (freq_avg - freq_lo) * dbs_data->sampling_rate;
        delay_hi_us += (freq_hi - freq_lo) / 2;
        delay_hi_us /= freq_hi - freq_lo;
        dbs_info->freq_hi_delay_us = delay_hi_us;
        dbs_info->freq_lo = freq_lo;
        dbs_info->freq_lo_delay_us = dbs_data->sampling_rate - delay_hi_us;
        return freq_hi;
}

static void ondemand_powersave_bias_init(struct cpufreq_policy *policy)
{
        struct od_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);

        dbs_info->freq_lo = 0;
}

static void dbs_freq_increase(struct cpufreq_policy *policy, unsigned int freq)
{
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct dbs_data *dbs_data = policy_dbs->dbs_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_update(struct cpufreq_policy *policy)
{
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct od_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
        struct dbs_data *dbs_data = policy_dbs->dbs_data;
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        unsigned int load = dbs_update(policy);

        dbs_info->freq_lo = 0;

        /* Check for frequency increase */
        if (load > dbs_data->up_threshold) {
                /* If switching to max speed, apply sampling_down_factor */
                if (policy->cur < policy->max)
                        policy_dbs->rate_mult = dbs_data->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 */
                policy_dbs->rate_mult = 1;

                if (od_tuners->powersave_bias)
                        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_update(struct cpufreq_policy *policy)
{
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct dbs_data *dbs_data = policy_dbs->dbs_data;
        struct od_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
        int sample_type = dbs_info->sample_type;

        /* Common NORMAL_SAMPLE setup */
        dbs_info->sample_type = OD_NORMAL_SAMPLE;
        /*
         * OD_SUB_SAMPLE doesn't make sense if sample_delay_ns is 0, so ignore
         * it then.
         */
        if (sample_type == OD_SUB_SAMPLE && policy_dbs->sample_delay_ns > 0) {
                __cpufreq_driver_target(policy, dbs_info->freq_lo,
                                        CPUFREQ_RELATION_H);
                return dbs_info->freq_lo_delay_us;
        }

        od_update(policy);

        if (dbs_info->freq_lo) {
                /* Setup SUB_SAMPLE */
                dbs_info->sample_type = OD_SUB_SAMPLE;
                return dbs_info->freq_hi_delay_us;
        }

        return dbs_data->sampling_rate * policy_dbs->rate_mult;
}

/************************** sysfs interface ************************/
static struct dbs_governor od_dbs_gov;

static ssize_t store_io_is_busy(struct gov_attr_set *attr_set, const char *buf,
                                size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        unsigned int input;
        int ret;

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

        /* we need to re-evaluate prev_cpu_idle */
        gov_update_cpu_data(dbs_data);

        return count;
}

static ssize_t store_up_threshold(struct gov_attr_set *attr_set,
                                  const char *buf, size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        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;
        }

        dbs_data->up_threshold = input;
        return count;
}

static ssize_t store_sampling_down_factor(struct gov_attr_set *attr_set,
                                          const char *buf, size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        struct policy_dbs_info *policy_dbs;
        unsigned int input;
        int ret;
        ret = sscanf(buf, "%u", &input);

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

        dbs_data->sampling_down_factor = input;

        /* Reset down sampling multiplier in case it was active */
        list_for_each_entry(policy_dbs, &attr_set->policy_list, list) {
                /*
                 * Doing this without locking might lead to using different
                 * rate_mult values in od_update() and od_dbs_update().
                 */
                mutex_lock(&policy_dbs->update_mutex);
                policy_dbs->rate_mult = 1;
                mutex_unlock(&policy_dbs->update_mutex);
        }

        return count;
}

static ssize_t store_ignore_nice_load(struct gov_attr_set *attr_set,
                                      const char *buf, size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        unsigned int input;
        int ret;

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

        if (input > 1)
                input = 1;

        if (input == dbs_data->ignore_nice_load) { /* nothing to do */
                return count;
        }
        dbs_data->ignore_nice_load = input;

        /* we need to re-evaluate prev_cpu_idle */
        gov_update_cpu_data(dbs_data);

        return count;
}

static ssize_t store_powersave_bias(struct gov_attr_set *attr_set,
                                    const char *buf, size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        struct od_dbs_tuners *od_tuners = dbs_data->tuners;
        struct policy_dbs_info *policy_dbs;
        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;

        list_for_each_entry(policy_dbs, &attr_set->policy_list, list)
                ondemand_powersave_bias_init(policy_dbs->policy);

        return count;
}

gov_show_one_common(sampling_rate);
gov_show_one_common(up_threshold);
gov_show_one_common(sampling_down_factor);
gov_show_one_common(ignore_nice_load);
gov_show_one_common(min_sampling_rate);
gov_show_one_common(io_is_busy);
gov_show_one(od, powersave_bias);

gov_attr_rw(sampling_rate);
gov_attr_rw(io_is_busy);
gov_attr_rw(up_threshold);
gov_attr_rw(sampling_down_factor);
gov_attr_rw(ignore_nice_load);
gov_attr_rw(powersave_bias);
gov_attr_ro(min_sampling_rate);

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

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

static struct policy_dbs_info *od_alloc(void)
{
        struct od_policy_dbs_info *dbs_info;

        dbs_info = kzalloc(sizeof(*dbs_info), GFP_KERNEL);
        return dbs_info ? &dbs_info->policy_dbs : NULL;
}

static void od_free(struct policy_dbs_info *policy_dbs)
{
        kfree(to_dbs_info(policy_dbs));
}

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

        tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
        if (!tuners)
                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 */
                dbs_data->up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
                /*
                 * In nohz/micro accounting case we set the minimum frequency
                 * not depending on HZ, but fixed (very low).
                */
                dbs_data->min_sampling_rate = MICRO_FREQUENCY_MIN_SAMPLE_RATE;
        } else {
                dbs_data->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);
        }

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

        dbs_data->tuners = tuners;
        return 0;
}

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

static void od_start(struct cpufreq_policy *policy)
{
        struct od_policy_dbs_info *dbs_info = to_dbs_info(policy->governor_data);

        dbs_info->sample_type = OD_NORMAL_SAMPLE;
        ondemand_powersave_bias_init(policy);
}

static struct od_ops od_ops = {
        .powersave_bias_target = generic_powersave_bias_target,
};

static struct dbs_governor od_dbs_gov = {
        .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("ondemand"),
        .kobj_type = { .default_attrs = od_attributes },
        .gov_dbs_update = od_dbs_update,
        .alloc = od_alloc,
        .free = od_free,
        .init = od_init,
        .exit = od_exit,
        .start = od_start,
};

#define CPU_FREQ_GOV_ONDEMAND   (&od_dbs_gov.gov)

static void od_set_powersave_bias(unsigned int powersave_bias)
{
        unsigned int cpu;
        cpumask_t done;

        default_powersave_bias = powersave_bias;
        cpumask_clear(&done);

        get_online_cpus();
        for_each_online_cpu(cpu) {
                struct cpufreq_policy *policy;
                struct policy_dbs_info *policy_dbs;
                struct dbs_data *dbs_data;
                struct od_dbs_tuners *od_tuners;

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

                policy = cpufreq_cpu_get_raw(cpu);
                if (!policy || policy->governor != CPU_FREQ_GOV_ONDEMAND)
                        continue;

                policy_dbs = policy->governor_data;
                if (!policy_dbs)
                        continue;

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

                dbs_data = policy_dbs->dbs_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 __init cpufreq_gov_dbs_init(void)
{
        return cpufreq_register_governor(CPU_FREQ_GOV_ONDEMAND);
}

static void __exit cpufreq_gov_dbs_exit(void)
{
        cpufreq_unregister_governor(CPU_FREQ_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
struct cpufreq_governor *cpufreq_default_governor(void)
{
        return CPU_FREQ_GOV_ONDEMAND;
}

fs_initcall(cpufreq_gov_dbs_init);
#else
module_init(cpufreq_gov_dbs_init);
#endif
module_exit(cpufreq_gov_dbs_exit);