/*
 * Generic Exynos Bus frequency driver with DEVFREQ Framework
 *
 * Copyright (c) 2016 Samsung Electronics Co., Ltd.
 * Author : Chanwoo Choi <cw00.choi@samsung.com>
 *
 * This driver support Exynos Bus frequency feature by using
 * DEVFREQ framework and is based on drivers/devfreq/exynos/exynos4_bus.c.
 *
 * 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/clk.h>
#include <linux/devfreq.h>
#include <linux/devfreq-event.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/pm_opp.h>
#include <linux/platform_device.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>

#define DEFAULT_SATURATION_RATIO        40
#define DEFAULT_VOLTAGE_TOLERANCE       2

struct exynos_bus {
        struct device *dev;

        struct devfreq *devfreq;
        struct devfreq_event_dev **edev;
        unsigned int edev_count;
        struct mutex lock;

        struct dev_pm_opp *curr_opp;

        struct regulator *regulator;
        struct clk *clk;
        unsigned int voltage_tolerance;
        unsigned int ratio;
};

/*
 * Control the devfreq-event device to get the current state of bus
 */
#define exynos_bus_ops_edev(ops)                                \
static int exynos_bus_##ops(struct exynos_bus *bus)             \
{                                                               \
        int i, ret;                                             \
                                                                \
        for (i = 0; i < bus->edev_count; i++) {                 \
                if (!bus->edev[i])                              \
                        continue;                               \
                ret = devfreq_event_##ops(bus->edev[i]);        \
                if (ret < 0)                                    \
                        return ret;                             \
        }                                                       \
                                                                \
        return 0;                                               \
}
exynos_bus_ops_edev(enable_edev);
exynos_bus_ops_edev(disable_edev);
exynos_bus_ops_edev(set_event);

static int exynos_bus_get_event(struct exynos_bus *bus,
                                struct devfreq_event_data *edata)
{
        struct devfreq_event_data event_data;
        unsigned long load_count = 0, total_count = 0;
        int i, ret = 0;

        for (i = 0; i < bus->edev_count; i++) {
                if (!bus->edev[i])
                        continue;

                ret = devfreq_event_get_event(bus->edev[i], &event_data);
                if (ret < 0)
                        return ret;

                if (i == 0 || event_data.load_count > load_count) {
                        load_count = event_data.load_count;
                        total_count = event_data.total_count;
                }
        }

        edata->load_count = load_count;
        edata->total_count = total_count;

        return ret;
}

/*
 * Must necessary function for devfreq simple-ondemand governor
 */
static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        struct dev_pm_opp *new_opp;
        unsigned long old_freq, new_freq, old_volt, new_volt, tol;
        int ret = 0;

        /* Get new opp-bus instance according to new bus clock */
        rcu_read_lock();
        new_opp = devfreq_recommended_opp(dev, freq, flags);
        if (IS_ERR(new_opp)) {
                dev_err(dev, "failed to get recommended opp instance\n");
                rcu_read_unlock();
                return PTR_ERR(new_opp);
        }

        new_freq = dev_pm_opp_get_freq(new_opp);
        new_volt = dev_pm_opp_get_voltage(new_opp);
        old_freq = dev_pm_opp_get_freq(bus->curr_opp);
        old_volt = dev_pm_opp_get_voltage(bus->curr_opp);
        rcu_read_unlock();

        if (old_freq == new_freq)
                return 0;
        tol = new_volt * bus->voltage_tolerance / 100;

        /* Change voltage and frequency according to new OPP level */
        mutex_lock(&bus->lock);

        if (old_freq < new_freq) {
                ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
                if (ret < 0) {
                        dev_err(bus->dev, "failed to set voltage\n");
                        goto out;
                }
        }

        ret = clk_set_rate(bus->clk, new_freq);
        if (ret < 0) {
                dev_err(dev, "failed to change clock of bus\n");
                clk_set_rate(bus->clk, old_freq);
                goto out;
        }

        if (old_freq > new_freq) {
                ret = regulator_set_voltage_tol(bus->regulator, new_volt, tol);
                if (ret < 0) {
                        dev_err(bus->dev, "failed to set voltage\n");
                        goto out;
                }
        }
        bus->curr_opp = new_opp;

        dev_dbg(dev, "Set the frequency of bus (%lukHz -> %lukHz)\n",
                        old_freq/1000, new_freq/1000);
out:
        mutex_unlock(&bus->lock);

        return ret;
}

static int exynos_bus_get_dev_status(struct device *dev,
                                     struct devfreq_dev_status *stat)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        struct devfreq_event_data edata;
        int ret;

        rcu_read_lock();
        stat->current_frequency = dev_pm_opp_get_freq(bus->curr_opp);
        rcu_read_unlock();

        ret = exynos_bus_get_event(bus, &edata);
        if (ret < 0) {
                stat->total_time = stat->busy_time = 0;
                goto err;
        }

        stat->busy_time = (edata.load_count * 100) / bus->ratio;
        stat->total_time = edata.total_count;

        dev_dbg(dev, "Usage of devfreq-event : %lu/%lu\n", stat->busy_time,
                                                        stat->total_time);

err:
        ret = exynos_bus_set_event(bus);
        if (ret < 0) {
                dev_err(dev, "failed to set event to devfreq-event devices\n");
                return ret;
        }

        return ret;
}

static void exynos_bus_exit(struct device *dev)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        int ret;

        ret = exynos_bus_disable_edev(bus);
        if (ret < 0)
                dev_warn(dev, "failed to disable the devfreq-event devices\n");

        if (bus->regulator)
                regulator_disable(bus->regulator);

        dev_pm_opp_of_remove_table(dev);
        clk_disable_unprepare(bus->clk);
}

/*
 * Must necessary function for devfreq passive governor
 */
static int exynos_bus_passive_target(struct device *dev, unsigned long *freq,
                                        u32 flags)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        struct dev_pm_opp *new_opp;
        unsigned long old_freq, new_freq;
        int ret = 0;

        /* Get new opp-bus instance according to new bus clock */
        rcu_read_lock();
        new_opp = devfreq_recommended_opp(dev, freq, flags);
        if (IS_ERR(new_opp)) {
                dev_err(dev, "failed to get recommended opp instance\n");
                rcu_read_unlock();
                return PTR_ERR(new_opp);
        }

        new_freq = dev_pm_opp_get_freq(new_opp);
        old_freq = dev_pm_opp_get_freq(bus->curr_opp);
        rcu_read_unlock();

        if (old_freq == new_freq)
                return 0;

        /* Change the frequency according to new OPP level */
        mutex_lock(&bus->lock);

        ret = clk_set_rate(bus->clk, new_freq);
        if (ret < 0) {
                dev_err(dev, "failed to set the clock of bus\n");
                goto out;
        }

        *freq = new_freq;
        bus->curr_opp = new_opp;

        dev_dbg(dev, "Set the frequency of bus (%lukHz -> %lukHz)\n",
                        old_freq/1000, new_freq/1000);
out:
        mutex_unlock(&bus->lock);

        return ret;
}

static void exynos_bus_passive_exit(struct device *dev)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);

        dev_pm_opp_of_remove_table(dev);
        clk_disable_unprepare(bus->clk);
}

static int exynos_bus_parent_parse_of(struct device_node *np,
                                        struct exynos_bus *bus)
{
        struct device *dev = bus->dev;
        int i, ret, count, size;

        /* Get the regulator to provide each bus with the power */
        bus->regulator = devm_regulator_get(dev, "vdd");
        if (IS_ERR(bus->regulator)) {
                dev_err(dev, "failed to get VDD regulator\n");
                return PTR_ERR(bus->regulator);
        }

        ret = regulator_enable(bus->regulator);
        if (ret < 0) {
                dev_err(dev, "failed to enable VDD regulator\n");
                return ret;
        }

        /*
         * Get the devfreq-event devices to get the current utilization of
         * buses. This raw data will be used in devfreq ondemand governor.
         */
        count = devfreq_event_get_edev_count(dev);
        if (count < 0) {
                dev_err(dev, "failed to get the count of devfreq-event dev\n");
                ret = count;
                goto err_regulator;
        }
        bus->edev_count = count;

        size = sizeof(*bus->edev) * count;
        bus->edev = devm_kzalloc(dev, size, GFP_KERNEL);
        if (!bus->edev) {
                ret = -ENOMEM;
                goto err_regulator;
        }

        for (i = 0; i < count; i++) {
                bus->edev[i] = devfreq_event_get_edev_by_phandle(dev, i);
                if (IS_ERR(bus->edev[i])) {
                        ret = -EPROBE_DEFER;
                        goto err_regulator;
                }
        }

        /*
         * Optionally, Get the saturation ratio according to Exynos SoC
         * When measuring the utilization of each AXI bus with devfreq-event
         * devices, the measured real cycle might be much lower than the
         * total cycle of bus during sampling rate. In result, the devfreq
         * simple-ondemand governor might not decide to change the current
         * frequency due to too utilization (= real cycle/total cycle).
         * So, this property is used to adjust the utilization when calculating
         * the busy_time in exynos_bus_get_dev_status().
         */
        if (of_property_read_u32(np, "exynos,saturation-ratio", &bus->ratio))
                bus->ratio = DEFAULT_SATURATION_RATIO;

        if (of_property_read_u32(np, "exynos,voltage-tolerance",
                                        &bus->voltage_tolerance))
                bus->voltage_tolerance = DEFAULT_VOLTAGE_TOLERANCE;

        return 0;

err_regulator:
        regulator_disable(bus->regulator);

        return ret;
}

static int exynos_bus_parse_of(struct device_node *np,
                              struct exynos_bus *bus)
{
        struct device *dev = bus->dev;
        unsigned long rate;
        int ret;

        /* Get the clock to provide each bus with source clock */
        bus->clk = devm_clk_get(dev, "bus");
        if (IS_ERR(bus->clk)) {
                dev_err(dev, "failed to get bus clock\n");
                return PTR_ERR(bus->clk);
        }

        ret = clk_prepare_enable(bus->clk);
        if (ret < 0) {
                dev_err(dev, "failed to get enable clock\n");
                return ret;
        }

        /* Get the freq and voltage from OPP table to scale the bus freq */
        rcu_read_lock();
        ret = dev_pm_opp_of_add_table(dev);
        if (ret < 0) {
                dev_err(dev, "failed to get OPP table\n");
                rcu_read_unlock();
                goto err_clk;
        }

        rate = clk_get_rate(bus->clk);
        bus->curr_opp = devfreq_recommended_opp(dev, &rate, 0);
        if (IS_ERR(bus->curr_opp)) {
                dev_err(dev, "failed to find dev_pm_opp\n");
                rcu_read_unlock();
                ret = PTR_ERR(bus->curr_opp);
                goto err_opp;
        }
        rcu_read_unlock();

        return 0;

err_opp:
        dev_pm_opp_of_remove_table(dev);
err_clk:
        clk_disable_unprepare(bus->clk);

        return ret;
}

static int exynos_bus_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *np = dev->of_node, *node;
        struct devfreq_dev_profile *profile;
        struct devfreq_simple_ondemand_data *ondemand_data;
        struct devfreq_passive_data *passive_data;
        struct devfreq *parent_devfreq;
        struct exynos_bus *bus;
        int ret, max_state;
        unsigned long min_freq, max_freq;

        if (!np) {
                dev_err(dev, "failed to find devicetree node\n");
                return -EINVAL;
        }

        bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
        if (!bus)
                return -ENOMEM;
        mutex_init(&bus->lock);
        bus->dev = &pdev->dev;
        platform_set_drvdata(pdev, bus);

        /* Parse the device-tree to get the resource information */
        ret = exynos_bus_parse_of(np, bus);
        if (ret < 0)
                return ret;

        profile = devm_kzalloc(dev, sizeof(*profile), GFP_KERNEL);
        if (!profile) {
                ret = -ENOMEM;
                goto err;
        }

        node = of_parse_phandle(dev->of_node, "devfreq", 0);
        if (node) {
                of_node_put(node);
                goto passive;
        } else {
                ret = exynos_bus_parent_parse_of(np, bus);
        }

        if (ret < 0)
                goto err;

        /* Initialize the struct profile and governor data for parent device */
        profile->polling_ms = 50;
        profile->target = exynos_bus_target;
        profile->get_dev_status = exynos_bus_get_dev_status;
        profile->exit = exynos_bus_exit;

        ondemand_data = devm_kzalloc(dev, sizeof(*ondemand_data), GFP_KERNEL);
        if (!ondemand_data) {
                ret = -ENOMEM;
                goto err;
        }
        ondemand_data->upthreshold = 40;
        ondemand_data->downdifferential = 5;

        /* Add devfreq device to monitor and handle the exynos bus */
        bus->devfreq = devm_devfreq_add_device(dev, profile, "simple_ondemand",
                                                ondemand_data);
        if (IS_ERR(bus->devfreq)) {
                dev_err(dev, "failed to add devfreq device\n");
                ret = PTR_ERR(bus->devfreq);
                goto err;
        }

        /* Register opp_notifier to catch the change of OPP  */
        ret = devm_devfreq_register_opp_notifier(dev, bus->devfreq);
        if (ret < 0) {
                dev_err(dev, "failed to register opp notifier\n");
                goto err;
        }

        /*
         * Enable devfreq-event to get raw data which is used to determine
         * current bus load.
         */
        ret = exynos_bus_enable_edev(bus);
        if (ret < 0) {
                dev_err(dev, "failed to enable devfreq-event devices\n");
                goto err;
        }

        ret = exynos_bus_set_event(bus);
        if (ret < 0) {
                dev_err(dev, "failed to set event to devfreq-event devices\n");
                goto err;
        }

        goto out;
passive:
        /* Initialize the struct profile and governor data for passive device */
        profile->target = exynos_bus_passive_target;
        profile->exit = exynos_bus_passive_exit;

        /* Get the instance of parent devfreq device */
        parent_devfreq = devfreq_get_devfreq_by_phandle(dev, 0);
        if (IS_ERR(parent_devfreq)) {
                ret = -EPROBE_DEFER;
                goto err;
        }

        passive_data = devm_kzalloc(dev, sizeof(*passive_data), GFP_KERNEL);
        if (!passive_data) {
                ret = -ENOMEM;
                goto err;
        }
        passive_data->parent = parent_devfreq;

        /* Add devfreq device for exynos bus with passive governor */
        bus->devfreq = devm_devfreq_add_device(dev, profile, "passive",
                                                passive_data);
        if (IS_ERR(bus->devfreq)) {
                dev_err(dev,
                        "failed to add devfreq dev with passive governor\n");
                ret = -EPROBE_DEFER;
                goto err;
        }

out:
        max_state = bus->devfreq->profile->max_state;
        min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
        max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
        pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
                        dev_name(dev), min_freq, max_freq);

        return 0;

err:
        dev_pm_opp_of_remove_table(dev);
        clk_disable_unprepare(bus->clk);

        return ret;
}

#ifdef CONFIG_PM_SLEEP
static int exynos_bus_resume(struct device *dev)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        int ret;

        ret = exynos_bus_enable_edev(bus);
        if (ret < 0) {
                dev_err(dev, "failed to enable the devfreq-event devices\n");
                return ret;
        }

        return 0;
}

static int exynos_bus_suspend(struct device *dev)
{
        struct exynos_bus *bus = dev_get_drvdata(dev);
        int ret;

        ret = exynos_bus_disable_edev(bus);
        if (ret < 0) {
                dev_err(dev, "failed to disable the devfreq-event devices\n");
                return ret;
        }

        return 0;
}
#endif

static const struct dev_pm_ops exynos_bus_pm = {
        SET_SYSTEM_SLEEP_PM_OPS(exynos_bus_suspend, exynos_bus_resume)
};

static const struct of_device_id exynos_bus_of_match[] = {
        { .compatible = "samsung,exynos-bus", },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, exynos_bus_of_match);

static struct platform_driver exynos_bus_platdrv = {
        .probe          = exynos_bus_probe,
        .driver = {
                .name   = "exynos-bus",
                .pm     = &exynos_bus_pm,
                .of_match_table = of_match_ptr(exynos_bus_of_match),
        },
};
module_platform_driver(exynos_bus_platdrv);

MODULE_DESCRIPTION("Generic Exynos Bus frequency driver");
MODULE_AUTHOR("Chanwoo Choi <cw00.choi@samsung.com>");
MODULE_LICENSE("GPL v2");