/*
 *  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/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>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/ktime.h>
#include <linux/sched.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 DEF_FREQUENCY_DOWN_THRESHOLD            (20)

/*
 * 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.
 */
#define MIN_SAMPLING_RATE_RATIO                 (2)

static unsigned int min_sampling_rate;

#define LATENCY_MULTIPLIER                      (1000)
#define MIN_LATENCY_MULTIPLIER                  (100)
#define DEF_SAMPLING_DOWN_FACTOR                (1)
#define MAX_SAMPLING_DOWN_FACTOR                (10)
#define TRANSITION_LATENCY_LIMIT                (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

struct cpu_dbs_info_s {
        cputime64_t prev_cpu_idle;
        cputime64_t prev_cpu_wall;
        cputime64_t prev_cpu_nice;
        struct cpufreq_policy *cur_policy;
        struct delayed_work work;
        unsigned int down_skip;
        unsigned int requested_freq;
        int cpu;
        unsigned int enable:1;
        /*
         * percpu mutex that serializes governor limit change with
         * do_dbs_timer invocation. We do not want do_dbs_timer to run
         * when user is changing the governor or limits.
         */
        struct mutex timer_mutex;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cs_cpu_dbs_info);

static unsigned int dbs_enable; /* number of CPUs using this policy */

/*
 * dbs_mutex protects dbs_enable in governor start/stop.
 */
static DEFINE_MUTEX(dbs_mutex);

static struct dbs_tuners {
        unsigned int sampling_rate;
        unsigned int sampling_down_factor;
        unsigned int up_threshold;
        unsigned int down_threshold;
        unsigned int ignore_nice;
        unsigned int freq_step;
} dbs_tuners_ins = {
        .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,
};

static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
{
        u64 idle_time;
        u64 cur_wall_time;
        u64 busy_time;

        cur_wall_time = jiffies64_to_cputime64(get_jiffies_64());

        busy_time  = kcpustat_cpu(cpu).cpustat[CPUTIME_USER];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SYSTEM];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_IRQ];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_SOFTIRQ];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_STEAL];
        busy_time += kcpustat_cpu(cpu).cpustat[CPUTIME_NICE];

        idle_time = cur_wall_time - busy_time;
        if (wall)
                *wall = jiffies_to_usecs(cur_wall_time);

        return jiffies_to_usecs(idle_time);
}

static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)
{
        u64 idle_time = get_cpu_idle_time_us(cpu, NULL);

        if (idle_time == -1ULL)
                return get_cpu_idle_time_jiffy(cpu, wall);
        else
                idle_time += get_cpu_iowait_time_us(cpu, wall);

        return idle_time;
}

/* keep track of frequency transitions */
static int
dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
                     void *data)
{
        struct cpufreq_freqs *freq = data;
        struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cs_cpu_dbs_info,
                                                        freq->cpu);

        struct cpufreq_policy *policy;

        if (!this_dbs_info->enable)
                return 0;

        policy = this_dbs_info->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 (this_dbs_info->requested_freq > policy->max
                        || this_dbs_info->requested_freq < policy->min)
                this_dbs_info->requested_freq = freq->new;

        return 0;
}

static struct notifier_block dbs_cpufreq_notifier_block = {
        .notifier_call = dbs_cpufreq_notifier
};

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

define_one_global_ro(sampling_rate_min);

/* cpufreq_conservative Governor Tunables */
#define show_one(file_name, object)                                     \
static ssize_t show_##file_name                                         \
(struct kobject *kobj, struct attribute *attr, char *buf)               \
{                                                                       \
        return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
}
show_one(sampling_rate, sampling_rate);
show_one(sampling_down_factor, sampling_down_factor);
show_one(up_threshold, up_threshold);
show_one(down_threshold, down_threshold);
show_one(ignore_nice_load, ignore_nice);
show_one(freq_step, freq_step);

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;

        dbs_tuners_ins.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;

        dbs_tuners_ins.sampling_rate = max(input, 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 <= dbs_tuners_ins.down_threshold)
                return -EINVAL;

        dbs_tuners_ins.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 >= dbs_tuners_ins.up_threshold)
                return -EINVAL;

        dbs_tuners_ins.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;
        int ret;

        unsigned int j;

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

        if (input > 1)
                input = 1;

        if (input == dbs_tuners_ins.ignore_nice) /* nothing to do */
                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(cs_cpu_dbs_info, j);
                dbs_info->prev_cpu_idle = get_cpu_idle_time(j,
                                                &dbs_info->prev_cpu_wall);
                if (dbs_tuners_ins.ignore_nice)
                        dbs_info->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 :) */
        dbs_tuners_ins.freq_step = input;
        return count;
}

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);

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 dbs_attr_group = {
        .attrs = dbs_attributes,
        .name = "conservative",
};

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

static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
{
        unsigned int load = 0;
        unsigned int max_load = 0;
        unsigned int freq_target;

        struct cpufreq_policy *policy;
        unsigned int j;

        policy = this_dbs_info->cur_policy;

        /*
         * 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
         */

        /* Get Absolute Load */
        for_each_cpu(j, policy->cpus) {
                struct cpu_dbs_info_s *j_dbs_info;
                cputime64_t cur_wall_time, cur_idle_time;
                unsigned int idle_time, wall_time;

                j_dbs_info = &per_cpu(cs_cpu_dbs_info, j);

                cur_idle_time = get_cpu_idle_time(j, &cur_wall_time);

                wall_time = (unsigned int)
                        (cur_wall_time - j_dbs_info->prev_cpu_wall);
                j_dbs_info->prev_cpu_wall = cur_wall_time;

                idle_time = (unsigned int)
                        (cur_idle_time - j_dbs_info->prev_cpu_idle);
                j_dbs_info->prev_cpu_idle = cur_idle_time;

                if (dbs_tuners_ins.ignore_nice) {
                        u64 cur_nice;
                        unsigned long cur_nice_jiffies;

                        cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
                                         j_dbs_info->prev_cpu_nice;
                        /*
                         * Assumption: nice time between sampling periods will
                         * be less than 2^32 jiffies for 32 bit sys
                         */
                        cur_nice_jiffies = (unsigned long)
                                        cputime64_to_jiffies64(cur_nice);

                        j_dbs_info->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
                        idle_time += jiffies_to_usecs(cur_nice_jiffies);
                }

                if (unlikely(!wall_time || wall_time < idle_time))
                        continue;

                load = 100 * (wall_time - idle_time) / wall_time;

                if (load > max_load)
                        max_load = load;
        }

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

        /* Check for frequency increase */
        if (max_load > dbs_tuners_ins.up_threshold) {
                this_dbs_info->down_skip = 0;

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

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

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

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

                __cpufreq_driver_target(policy, this_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 (max_load < (dbs_tuners_ins.down_threshold - 10)) {
                freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100;

                this_dbs_info->requested_freq -= freq_target;
                if (this_dbs_info->requested_freq < policy->min)
                        this_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, this_dbs_info->requested_freq,
                                CPUFREQ_RELATION_H);
                return;
        }
}

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;

        /* We want all CPUs to do sampling nearly on same jiffy */
        int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

        delay -= jiffies % delay;

        mutex_lock(&dbs_info->timer_mutex);

        dbs_check_cpu(dbs_info);

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

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;
        INIT_DEFERRABLE_WORK(&dbs_info->work, do_dbs_timer);
        schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
}

static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
{
        dbs_info->enable = 0;
        cancel_delayed_work_sync(&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(cs_cpu_dbs_info, cpu);

        switch (event) {
        case CPUFREQ_GOV_START:
                if ((!cpu_online(cpu)) || (!policy->cur))
                        return -EINVAL;

                mutex_lock(&dbs_mutex);

                for_each_cpu(j, policy->cpus) {
                        struct cpu_dbs_info_s *j_dbs_info;
                        j_dbs_info = &per_cpu(cs_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);
                        if (dbs_tuners_ins.ignore_nice)
                                j_dbs_info->prev_cpu_nice =
                                                kcpustat_cpu(j).cpustat[CPUTIME_NICE];
                }
                this_dbs_info->cpu = cpu;
                this_dbs_info->down_skip = 0;
                this_dbs_info->requested_freq = policy->cur;

                mutex_init(&this_dbs_info->timer_mutex);
                dbs_enable++;
                /*
                 * 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;

                        rc = sysfs_create_group(cpufreq_global_kobject,
                                                &dbs_attr_group);
                        if (rc) {
                                mutex_unlock(&dbs_mutex);
                                return rc;
                        }

                        /*
                         * conservative does not implement micro like ondemand
                         * governor, thus we are bound to jiffes/HZ
                         */
                        min_sampling_rate =
                                MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
                        /* Bring kernel and HW constraints together */
                        min_sampling_rate = max(min_sampling_rate,
                                        MIN_LATENCY_MULTIPLIER * latency);
                        dbs_tuners_ins.sampling_rate =
                                max(min_sampling_rate,
                                    latency * LATENCY_MULTIPLIER);

                        cpufreq_register_notifier(
                                        &dbs_cpufreq_notifier_block,
                                        CPUFREQ_TRANSITION_NOTIFIER);
                }
                mutex_unlock(&dbs_mutex);

                dbs_timer_init(this_dbs_info);

                break;

        case CPUFREQ_GOV_STOP:
                dbs_timer_exit(this_dbs_info);

                mutex_lock(&dbs_mutex);
                dbs_enable--;
                mutex_destroy(&this_dbs_info->timer_mutex);

                /*
                 * Stop the timerschedule work, when this governor
                 * is used for first time
                 */
                if (dbs_enable == 0)
                        cpufreq_unregister_notifier(
                                        &dbs_cpufreq_notifier_block,
                                        CPUFREQ_TRANSITION_NOTIFIER);

                mutex_unlock(&dbs_mutex);
                if (!dbs_enable)
                        sysfs_remove_group(cpufreq_global_kobject,
                                           &dbs_attr_group);

                break;

        case CPUFREQ_GOV_LIMITS:
                mutex_lock(&this_dbs_info->timer_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);
                dbs_check_cpu(this_dbs_info);
                mutex_unlock(&this_dbs_info->timer_mutex);

                break;
        }
        return 0;
}

#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
static
#endif
struct cpufreq_governor cpufreq_gov_conservative = {
        .name                   = "conservative",
        .governor               = 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_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);