// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
/*
 * Copyright (c) 2016 BayLibre, SAS.
 * Author: Neil Armstrong <narmstrong@baylibre.com>
 * Copyright (C) 2014 Amlogic, Inc.
 */
#include <linux/err.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/of.h>
#include <linux/clk.h>
#include <linux/iopoll.h>

#define RNG_DATA        0x00
#define RNG_S4_DATA     0x08
#define RNG_S4_CFG      0x00

#define RUN_BIT         BIT(0)
#define SEED_READY_STS_BIT      BIT(31)

struct meson_rng_priv {
        int (*read)(struct hwrng *rng, void *buf, size_t max, bool wait);
};

struct meson_rng_data {
        void __iomem *base;
        struct hwrng rng;
        struct device *dev;
};

static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
        struct meson_rng_data *data =
                        container_of(rng, struct meson_rng_data, rng);

        *(u32 *)buf = readl_relaxed(data->base + RNG_DATA);

        return sizeof(u32);
}

static int meson_rng_wait_status(void __iomem *cfg_addr, int bit)
{
        u32 status = 0;
        int ret;

        ret = readl_relaxed_poll_timeout_atomic(cfg_addr,
                                                status, !(status & bit),
                                                10, 10000);
        if (ret)
                return -EBUSY;

        return 0;
}

static int meson_s4_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
        struct meson_rng_data *data =
                        container_of(rng, struct meson_rng_data, rng);

        void __iomem *cfg_addr = data->base + RNG_S4_CFG;
        int err;

        writel_relaxed(readl_relaxed(cfg_addr) | SEED_READY_STS_BIT, cfg_addr);

        err = meson_rng_wait_status(cfg_addr, SEED_READY_STS_BIT);
        if (err) {
                dev_err(data->dev, "Seed isn't ready, try again\n");
                return err;
        }

        err = meson_rng_wait_status(cfg_addr, RUN_BIT);
        if (err) {
                dev_err(data->dev, "Can't get random number, try again\n");
                return err;
        }

        *(u32 *)buf = readl_relaxed(data->base + RNG_S4_DATA);

        return sizeof(u32);
}

static int meson_rng_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct meson_rng_data *data;
        struct clk *core_clk;
        const struct meson_rng_priv *priv;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        priv = device_get_match_data(&pdev->dev);
        if (!priv)
                return -ENODEV;

        data->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(data->base))
                return PTR_ERR(data->base);

        core_clk = devm_clk_get_optional_enabled(dev, "core");
        if (IS_ERR(core_clk))
                return dev_err_probe(dev, PTR_ERR(core_clk),
                                     "Failed to get core clock\n");

        data->rng.name = pdev->name;
        data->rng.read = priv->read;

        data->dev = &pdev->dev;

        return devm_hwrng_register(dev, &data->rng);
}

static const struct meson_rng_priv meson_rng_priv = {
        .read = meson_rng_read,
};

static const struct meson_rng_priv meson_rng_priv_s4 = {
        .read = meson_s4_rng_read,
};

static const struct of_device_id meson_rng_of_match[] = {
        {
                .compatible = "amlogic,meson-rng",
                .data = (void *)&meson_rng_priv,
        },
        {
                .compatible = "amlogic,meson-s4-rng",
                .data = (void *)&meson_rng_priv_s4,
        },
        {},
};
MODULE_DEVICE_TABLE(of, meson_rng_of_match);

static struct platform_driver meson_rng_driver = {
        .probe  = meson_rng_probe,
        .driver = {
                .name = "meson-rng",
                .of_match_table = meson_rng_of_match,
        },
};

module_platform_driver(meson_rng_driver);

MODULE_DESCRIPTION("Meson H/W Random Number Generator driver");
MODULE_AUTHOR("Lawrence Mok <lawrence.mok@amlogic.com>");
MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
MODULE_LICENSE("Dual BSD/GPL");