// SPDX-License-Identifier: GPL-2.0
/*
 * NVIDIA Tegra20 devfreq driver
 *
 * Copyright (C) 2019 GRATE-DRIVER project
 */

#include <linux/clk.h>
#include <linux/devfreq.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm_opp.h>
#include <linux/slab.h>

#include <soc/tegra/mc.h>

#include "governor.h"

#define MC_STAT_CONTROL                         0x90
#define MC_STAT_EMC_CLOCK_LIMIT                 0xa0
#define MC_STAT_EMC_CLOCKS                      0xa4
#define MC_STAT_EMC_CONTROL                     0xa8
#define MC_STAT_EMC_COUNT                       0xb8

#define EMC_GATHER_CLEAR                        (1 << 8)
#define EMC_GATHER_ENABLE                       (3 << 8)

struct tegra_devfreq {
        struct devfreq *devfreq;
        struct clk *emc_clock;
        void __iomem *regs;
};

static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
                                u32 flags)
{
        struct tegra_devfreq *tegra = dev_get_drvdata(dev);
        struct devfreq *devfreq = tegra->devfreq;
        struct dev_pm_opp *opp;
        unsigned long rate;
        int err;

        opp = devfreq_recommended_opp(dev, freq, flags);
        if (IS_ERR(opp))
                return PTR_ERR(opp);

        rate = dev_pm_opp_get_freq(opp);
        dev_pm_opp_put(opp);

        err = clk_set_min_rate(tegra->emc_clock, rate);
        if (err)
                return err;

        err = clk_set_rate(tegra->emc_clock, 0);
        if (err)
                goto restore_min_rate;

        return 0;

restore_min_rate:
        clk_set_min_rate(tegra->emc_clock, devfreq->previous_freq);

        return err;
}

static int tegra_devfreq_get_dev_status(struct device *dev,
                                        struct devfreq_dev_status *stat)
{
        struct tegra_devfreq *tegra = dev_get_drvdata(dev);

        /*
         * EMC_COUNT returns number of memory events, that number is lower
         * than the number of clocks. Conversion ratio of 1/8 results in a
         * bit higher bandwidth than actually needed, it is good enough for
         * the time being because drivers don't support requesting minimum
         * needed memory bandwidth yet.
         *
         * TODO: adjust the ratio value once relevant drivers will support
         * memory bandwidth management.
         */
        stat->busy_time = readl_relaxed(tegra->regs + MC_STAT_EMC_COUNT);
        stat->total_time = readl_relaxed(tegra->regs + MC_STAT_EMC_CLOCKS) / 8;
        stat->current_frequency = clk_get_rate(tegra->emc_clock);

        writel_relaxed(EMC_GATHER_CLEAR, tegra->regs + MC_STAT_CONTROL);
        writel_relaxed(EMC_GATHER_ENABLE, tegra->regs + MC_STAT_CONTROL);

        return 0;
}

static struct devfreq_dev_profile tegra_devfreq_profile = {
        .polling_ms     = 500,
        .target         = tegra_devfreq_target,
        .get_dev_status = tegra_devfreq_get_dev_status,
};

static struct tegra_mc *tegra_get_memory_controller(void)
{
        struct platform_device *pdev;
        struct device_node *np;
        struct tegra_mc *mc;

        np = of_find_compatible_node(NULL, NULL, "nvidia,tegra20-mc-gart");
        if (!np)
                return ERR_PTR(-ENOENT);

        pdev = of_find_device_by_node(np);
        of_node_put(np);
        if (!pdev)
                return ERR_PTR(-ENODEV);

        mc = platform_get_drvdata(pdev);
        if (!mc)
                return ERR_PTR(-EPROBE_DEFER);

        return mc;
}

static int tegra_devfreq_probe(struct platform_device *pdev)
{
        struct tegra_devfreq *tegra;
        struct tegra_mc *mc;
        unsigned long max_rate;
        unsigned long rate;
        int err;

        mc = tegra_get_memory_controller();
        if (IS_ERR(mc)) {
                err = PTR_ERR(mc);
                dev_err(&pdev->dev, "failed to get memory controller: %d\n",
                        err);
                return err;
        }

        tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
        if (!tegra)
                return -ENOMEM;

        /* EMC is a system-critical clock that is always enabled */
        tegra->emc_clock = devm_clk_get(&pdev->dev, "emc");
        if (IS_ERR(tegra->emc_clock)) {
                err = PTR_ERR(tegra->emc_clock);
                dev_err(&pdev->dev, "failed to get emc clock: %d\n", err);
                return err;
        }

        tegra->regs = mc->regs;

        max_rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);

        for (rate = 0; rate <= max_rate; rate++) {
                rate = clk_round_rate(tegra->emc_clock, rate);

                err = dev_pm_opp_add(&pdev->dev, rate, 0);
                if (err) {
                        dev_err(&pdev->dev, "failed to add opp: %d\n", err);
                        goto remove_opps;
                }
        }

        /*
         * Reset statistic gathers state, select global bandwidth for the
         * statistics collection mode and set clocks counter saturation
         * limit to maximum.
         */
        writel_relaxed(0x00000000, tegra->regs + MC_STAT_CONTROL);
        writel_relaxed(0x00000000, tegra->regs + MC_STAT_EMC_CONTROL);
        writel_relaxed(0xffffffff, tegra->regs + MC_STAT_EMC_CLOCK_LIMIT);

        platform_set_drvdata(pdev, tegra);

        tegra->devfreq = devfreq_add_device(&pdev->dev, &tegra_devfreq_profile,
                                            DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
        if (IS_ERR(tegra->devfreq)) {
                err = PTR_ERR(tegra->devfreq);
                goto remove_opps;
        }

        return 0;

remove_opps:
        dev_pm_opp_remove_all_dynamic(&pdev->dev);

        return err;
}

static int tegra_devfreq_remove(struct platform_device *pdev)
{
        struct tegra_devfreq *tegra = platform_get_drvdata(pdev);

        devfreq_remove_device(tegra->devfreq);
        dev_pm_opp_remove_all_dynamic(&pdev->dev);

        return 0;
}

static struct platform_driver tegra_devfreq_driver = {
        .probe          = tegra_devfreq_probe,
        .remove         = tegra_devfreq_remove,
        .driver         = {
                .name   = "tegra20-devfreq",
        },
};
module_platform_driver(tegra_devfreq_driver);

MODULE_ALIAS("platform:tegra20-devfreq");
MODULE_AUTHOR("Dmitry Osipenko <digetx@gmail.com>");
MODULE_DESCRIPTION("NVIDIA Tegra20 devfreq driver");
MODULE_LICENSE("GPL v2");