// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/drivers/devfreq/governor_simpleondemand.c
 *
 *  Copyright (C) 2011 Samsung Electronics
 *      MyungJoo Ham <myungjoo.ham@samsung.com>
 */

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/devfreq.h>
#include <linux/devfreq-governor.h>
#include <linux/math64.h>

/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
#define DFSO_UPTHRESHOLD        (90)
#define DFSO_DOWNDIFFERENTIAL   (5)
static int devfreq_simple_ondemand_func(struct devfreq *df,
                                        unsigned long *freq)
{
        int err;
        struct devfreq_dev_status *stat;
        unsigned long long a, b;
        unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
        unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENTIAL;
        struct devfreq_simple_ondemand_data *data = df->data;

        err = devfreq_update_stats(df);
        if (err)
                return err;

        stat = &df->last_status;

        if (data) {
                if (data->upthreshold)
                        dfso_upthreshold = data->upthreshold;
                if (data->downdifferential)
                        dfso_downdifferential = data->downdifferential;
        }
        if (dfso_upthreshold > 100 ||
            dfso_upthreshold < dfso_downdifferential)
                return -EINVAL;

        /* Assume MAX if it is going to be divided by zero */
        if (stat->total_time == 0) {
                *freq = DEVFREQ_MAX_FREQ;
                return 0;
        }

        /* Prevent overflow */
        if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
                stat->busy_time >>= 7;
                stat->total_time >>= 7;
        }

        /* Set MAX if it's busy enough */
        if (stat->busy_time * 100 >
            stat->total_time * dfso_upthreshold) {
                *freq = DEVFREQ_MAX_FREQ;
                return 0;
        }

        /* Set MAX if we do not know the initial frequency */
        if (stat->current_frequency == 0) {
                *freq = DEVFREQ_MAX_FREQ;
                return 0;
        }

        /* Keep the current frequency */
        if (stat->busy_time * 100 >
            stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
                *freq = stat->current_frequency;
                return 0;
        }

        /* Set the desired frequency based on the load */
        a = stat->busy_time;
        a *= stat->current_frequency;
        b = div_u64(a, stat->total_time);
        b *= 100;
        b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
        *freq = (unsigned long) b;

        return 0;
}

static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
                                unsigned int event, void *data)
{
        switch (event) {
        case DEVFREQ_GOV_START:
                devfreq_monitor_start(devfreq);
                break;

        case DEVFREQ_GOV_STOP:
                devfreq_monitor_stop(devfreq);
                break;

        case DEVFREQ_GOV_UPDATE_INTERVAL:
                devfreq_update_interval(devfreq, (unsigned int *)data);
                break;

        case DEVFREQ_GOV_SUSPEND:
                devfreq_monitor_suspend(devfreq);
                break;

        case DEVFREQ_GOV_RESUME:
                devfreq_monitor_resume(devfreq);
                break;

        default:
                break;
        }

        return 0;
}

static struct devfreq_governor devfreq_simple_ondemand = {
        .name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
        .attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
                | DEVFREQ_GOV_ATTR_TIMER,
        .get_target_freq = devfreq_simple_ondemand_func,
        .event_handler = devfreq_simple_ondemand_handler,
};

static int __init devfreq_simple_ondemand_init(void)
{
        return devfreq_add_governor(&devfreq_simple_ondemand);
}
subsys_initcall(devfreq_simple_ondemand_init);

static void __exit devfreq_simple_ondemand_exit(void)
{
        int ret;

        ret = devfreq_remove_governor(&devfreq_simple_ondemand);
        if (ret)
                pr_err("%s: failed remove governor %d\n", __func__, ret);

        return;
}
module_exit(devfreq_simple_ondemand_exit);
MODULE_DESCRIPTION("DEVFREQ Simple On-demand governor");
MODULE_LICENSE("GPL");