/*
 *  drivers/cpufreq/cpufreq_conservative.c
 *
 *  Copyright (C)  2001 Russell King
 *            (C)  2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
 *                      Jun Nakajima <jun.nakajima@intel.com>
 *            (C)  2009 Alexander Clouter <alex@digriz.org.uk>
 *
 * 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/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/notifier.h>
#include <linux/percpu-defs.h>
#include <linux/sysfs.h>
#include <linux/types.h>

#include "cpufreq_governor.h"

/* Conservative governor macors */
#define DEF_FREQUENCY_UP_THRESHOLD              (80)
#define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
#define DEF_SAMPLING_DOWN_FACTOR                (1)
#define MAX_SAMPLING_DOWN_FACTOR                (10)

static struct dbs_data cs_dbs_data;
static DEFINE_PER_CPU(struct cs_cpu_dbs_info_s, cs_cpu_dbs_info);

static struct cs_dbs_tuners cs_tuners = {
        .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
        .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
        .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
        .ignore_nice = 0,
        .freq_step = 5,
};

/*
 * Every sampling_rate, we check, if current idle time is less than 20%
 * (default), then we try to increase frequency Every sampling_rate *
 * sampling_down_factor, we check, if current idle time is more than 80%, then
 * we try to decrease frequency
 *
 * Any frequency increase takes it to the maximum frequency. Frequency reduction
 * happens at minimum steps of 5% (default) of maximum frequency
 */
static void cs_check_cpu(int cpu, unsigned int load)
{
        struct cs_cpu_dbs_info_s *dbs_info = &per_cpu(cs_cpu_dbs_info, cpu);
        struct cpufreq_policy *policy = dbs_info->cdbs.cur_policy;
        unsigned int freq_target;

        /*
         * break out if we 'cannot' reduce the speed as the user might
         * want freq_step to be zero
         */
        if (cs_tuners.freq_step == 0)
                return;

        /* Check for frequency increase */
        if (load > cs_tuners.up_threshold) {
                dbs_info->down_skip = 0;

                /* if we are already at full speed then break out early */
                if (dbs_info->requested_freq == policy->max)
                        return;

                freq_target = (cs_tuners.freq_step * policy->max) / 100;

                /* max freq cannot be less than 100. But who knows.... */
                if (unlikely(freq_target == 0))
                        freq_target = 5;

                dbs_info->requested_freq += freq_target;
                if (dbs_info->requested_freq > policy->max)
                        dbs_info->requested_freq = policy->max;

                __cpufreq_driver_target(policy, dbs_info->requested_freq,
                        CPUFREQ_RELATION_H);
                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 < (cs_tuners.down_threshold - 10)) {
                freq_target = (cs_tuners.freq_step * policy->max) / 100;

                dbs_info->requested_freq -= freq_target;
                if (dbs_info->requested_freq < policy->min)
                        dbs_info->requested_freq = policy->min;

                /*
                 * if we cannot reduce the frequency anymore, break out early
                 */
                if (policy->cur == policy->min)
                        return;

                __cpufreq_driver_target(policy, dbs_info->requested_freq,
                                CPUFREQ_RELATION_H);
                return;
        }
}

static void cs_dbs_timer(struct work_struct *work)
{
        struct cs_cpu_dbs_info_s *dbs_info = container_of(work,
                        struct cs_cpu_dbs_info_s, cdbs.work.work);
        unsigned int cpu = dbs_info->cdbs.cpu;
        int delay = delay_for_sampling_rate(cs_tuners.sampling_rate);

        mutex_lock(&dbs_info->cdbs.timer_mutex);

        dbs_check_cpu(&cs_dbs_data, cpu);

        schedule_delayed_work_on(cpu, &dbs_info->cdbs.work, delay);
        mutex_unlock(&dbs_info->cdbs.timer_mutex);
}

static int dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
                void *data)
{
        struct cpufreq_freqs *freq = data;
        struct cs_cpu_dbs_info_s *dbs_info =
                                        &per_cpu(cs_cpu_dbs_info, freq->cpu);
        struct cpufreq_policy *policy;

        if (!dbs_info->enable)
                return 0;

        policy = dbs_info->cdbs.cur_policy;

        /*
         * we only care if our internally tracked freq moves outside the 'valid'
         * ranges of freqency available to us otherwise we do not change it
        */
        if (dbs_info->requested_freq > policy->max
                        || dbs_info->requested_freq < policy->min)
                dbs_info->requested_freq = freq->new;

        return 0;
}

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

static ssize_t store_sampling_down_factor(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_SAMPLING_DOWN_FACTOR || input < 1)
                return -EINVAL;

        cs_tuners.sampling_down_factor = input;
        return count;
}

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;

        cs_tuners.sampling_rate = max(input, cs_dbs_data.min_sampling_rate);
        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 > 100 || input <= cs_tuners.down_threshold)
                return -EINVAL;

        cs_tuners.up_threshold = input;
        return count;
}

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

        /* cannot be lower than 11 otherwise freq will not fall */
        if (ret != 1 || input < 11 || input > 100 ||
                        input >= cs_tuners.up_threshold)
                return -EINVAL;

        cs_tuners.down_threshold = input;
        return count;
}

static ssize_t store_ignore_nice_load(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)
                return -EINVAL;

        if (input > 1)
                input = 1;

        if (input == cs_tuners.ignore_nice) /* nothing to do */
                return count;

        cs_tuners.ignore_nice = input;

        /* we need to re-evaluate prev_cpu_idle */
        for_each_online_cpu(j) {
                struct cs_cpu_dbs_info_s *dbs_info;
                dbs_info = &per_cpu(cs_cpu_dbs_info, j);
                dbs_info->cdbs.prev_cpu_idle = get_cpu_idle_time(j,
                                                &dbs_info->cdbs.prev_cpu_wall);
                if (cs_tuners.ignore_nice)
                        dbs_info->cdbs.prev_cpu_nice =
                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];
        }
        return count;
}

static ssize_t store_freq_step(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 > 100)
                input = 100;

        /*
         * no need to test here if freq_step is zero as the user might actually
         * want this, they would be crazy though :)
         */
        cs_tuners.freq_step = input;
        return count;
}

show_one(cs, sampling_rate, sampling_rate);
show_one(cs, sampling_down_factor, sampling_down_factor);
show_one(cs, up_threshold, up_threshold);
show_one(cs, down_threshold, down_threshold);
show_one(cs, ignore_nice_load, ignore_nice);
show_one(cs, freq_step, freq_step);

define_one_global_rw(sampling_rate);
define_one_global_rw(sampling_down_factor);
define_one_global_rw(up_threshold);
define_one_global_rw(down_threshold);
define_one_global_rw(ignore_nice_load);
define_one_global_rw(freq_step);
define_one_global_ro(sampling_rate_min);

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

static struct attribute_group cs_attr_group = {
        .attrs = dbs_attributes,
        .name = "conservative",
};

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

define_get_cpu_dbs_routines(cs_cpu_dbs_info);

static struct notifier_block cs_cpufreq_notifier_block = {
        .notifier_call = dbs_cpufreq_notifier,
};

static struct cs_ops cs_ops = {
        .notifier_block = &cs_cpufreq_notifier_block,
};

static struct dbs_data cs_dbs_data = {
        .governor = GOV_CONSERVATIVE,
        .attr_group = &cs_attr_group,
        .tuners = &cs_tuners,
        .get_cpu_cdbs = get_cpu_cdbs,
        .get_cpu_dbs_info_s = get_cpu_dbs_info_s,
        .gov_dbs_timer = cs_dbs_timer,
        .gov_check_cpu = cs_check_cpu,
        .gov_ops = &cs_ops,
};

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

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
static
#endif
struct cpufreq_governor cpufreq_gov_conservative = {
        .name                   = "conservative",
        .governor               = cs_cpufreq_governor_dbs,
        .max_transition_latency = TRANSITION_LATENCY_LIMIT,
        .owner                  = THIS_MODULE,
};

static int __init cpufreq_gov_dbs_init(void)
{
        mutex_init(&cs_dbs_data.mutex);
        return cpufreq_register_governor(&cpufreq_gov_conservative);
}

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

MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
MODULE_DESCRIPTION("'cpufreq_conservative' - A dynamic cpufreq governor for "
                "Low Latency Frequency Transition capable processors "
                "optimised for use in a battery environment");
MODULE_LICENSE("GPL");

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