/*
 *  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/slab.h>
#include "cpufreq_governor.h"

struct cs_policy_dbs_info {
        struct policy_dbs_info policy_dbs;
        unsigned int down_skip;
        unsigned int requested_freq;
};

static inline struct cs_policy_dbs_info *to_dbs_info(struct policy_dbs_info *policy_dbs)
{
        return container_of(policy_dbs, struct cs_policy_dbs_info, policy_dbs);
}

struct cs_dbs_tuners {
        unsigned int down_threshold;
        unsigned int freq_step;
};

/* Conservative governor macros */
#define DEF_FREQUENCY_UP_THRESHOLD              (80)
#define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
#define DEF_FREQUENCY_STEP                      (5)
#define DEF_SAMPLING_DOWN_FACTOR                (1)
#define MAX_SAMPLING_DOWN_FACTOR                (10)

static inline unsigned int get_freq_step(struct cs_dbs_tuners *cs_tuners,
                                         struct cpufreq_policy *policy)
{
        unsigned int freq_step = (cs_tuners->freq_step * policy->max) / 100;

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

        return freq_step;
}

/*
 * 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%
 * (default), then we try to decrease frequency
 *
 * Frequency updates happen at minimum steps of 5% (default) of maximum
 * frequency
 */
static unsigned int cs_dbs_update(struct cpufreq_policy *policy)
{
        struct policy_dbs_info *policy_dbs = policy->governor_data;
        struct cs_policy_dbs_info *dbs_info = to_dbs_info(policy_dbs);
        unsigned int requested_freq = dbs_info->requested_freq;
        struct dbs_data *dbs_data = policy_dbs->dbs_data;
        struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
        unsigned int load = dbs_update(policy);
        unsigned int freq_step;

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

        /*
         * If requested_freq is out of range, it is likely that the limits
         * changed in the meantime, so fall back to current frequency in that
         * case.
         */
        if (requested_freq > policy->max || requested_freq < policy->min)
                requested_freq = policy->cur;

        freq_step = get_freq_step(cs_tuners, policy);

        /*
         * Decrease requested_freq one freq_step for each idle period that
         * we didn't update the frequency.
         */
        if (policy_dbs->idle_periods < UINT_MAX) {
                unsigned int freq_steps = policy_dbs->idle_periods * freq_step;

                if (requested_freq > freq_steps)
                        requested_freq -= freq_steps;
                else
                        requested_freq = policy->min;

                policy_dbs->idle_periods = UINT_MAX;
        }

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

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

                requested_freq += freq_step;
                if (requested_freq > policy->max)
                        requested_freq = policy->max;

                __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H);
                dbs_info->requested_freq = requested_freq;
                goto out;
        }

        /* if sampling_down_factor is active break out early */
        if (++dbs_info->down_skip < dbs_data->sampling_down_factor)
                goto out;
        dbs_info->down_skip = 0;

        /* Check for frequency decrease */
        if (load < cs_tuners->down_threshold) {
                /*
                 * if we cannot reduce the frequency anymore, break out early
                 */
                if (requested_freq == policy->min)
                        goto out;

                if (requested_freq > freq_step)
                        requested_freq -= freq_step;
                else
                        requested_freq = policy->min;

                __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L);
                dbs_info->requested_freq = requested_freq;
        }

 out:
        return dbs_data->sampling_rate;
}

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

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);
        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;
        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);
        struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
        unsigned int input;
        int ret;
        ret = sscanf(buf, "%u", &input);

        if (ret != 1 || input > 100 || input <= cs_tuners->down_threshold)
                return -EINVAL;

        dbs_data->up_threshold = input;
        return count;
}

static ssize_t store_down_threshold(struct gov_attr_set *attr_set,
                                    const char *buf, size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
        unsigned int input;
        int ret;
        ret = sscanf(buf, "%u", &input);

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

        cs_tuners->down_threshold = input;
        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_freq_step(struct gov_attr_set *attr_set, const char *buf,
                               size_t count)
{
        struct dbs_data *dbs_data = to_dbs_data(attr_set);
        struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
        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;
}

gov_show_one_common(sampling_rate);
gov_show_one_common(sampling_down_factor);
gov_show_one_common(up_threshold);
gov_show_one_common(ignore_nice_load);
gov_show_one(cs, down_threshold);
gov_show_one(cs, freq_step);

gov_attr_rw(sampling_rate);
gov_attr_rw(sampling_down_factor);
gov_attr_rw(up_threshold);
gov_attr_rw(ignore_nice_load);
gov_attr_rw(down_threshold);
gov_attr_rw(freq_step);

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

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

static struct policy_dbs_info *cs_alloc(void)
{
        struct cs_policy_dbs_info *dbs_info;

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

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

static int cs_init(struct dbs_data *dbs_data)
{
        struct cs_dbs_tuners *tuners;

        tuners = kzalloc(sizeof(*tuners), GFP_KERNEL);
        if (!tuners)
                return -ENOMEM;

        tuners->down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD;
        tuners->freq_step = DEF_FREQUENCY_STEP;
        dbs_data->up_threshold = DEF_FREQUENCY_UP_THRESHOLD;
        dbs_data->sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR;
        dbs_data->ignore_nice_load = 0;
        dbs_data->tuners = tuners;

        return 0;
}

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

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

        dbs_info->down_skip = 0;
        dbs_info->requested_freq = policy->cur;
}

static struct dbs_governor cs_governor = {
        .gov = CPUFREQ_DBS_GOVERNOR_INITIALIZER("conservative"),
        .kobj_type = { .default_attrs = cs_attributes },
        .gov_dbs_update = cs_dbs_update,
        .alloc = cs_alloc,
        .free = cs_free,
        .init = cs_init,
        .exit = cs_exit,
        .start = cs_start,
};

#define CPU_FREQ_GOV_CONSERVATIVE       (&cs_governor.gov)

static int __init cpufreq_gov_dbs_init(void)
{
        return cpufreq_register_governor(CPU_FREQ_GOV_CONSERVATIVE);
}

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

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