// SPDX-License-Identifier: GPL-2.0
/*
 * Ingenic Random Number Generator driver
 * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
 * Copyright (c) 2020 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
 */

#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

/* RNG register offsets */
#define RNG_REG_ERNG_OFFSET             0x0
#define RNG_REG_RNG_OFFSET              0x4

/* bits within the ERND register */
#define ERNG_READY                              BIT(31)
#define ERNG_ENABLE                             BIT(0)

enum ingenic_rng_version {
        ID_JZ4780,
        ID_X1000,
};

/* Device associated memory */
struct ingenic_rng {
        enum ingenic_rng_version version;

        void __iomem *base;
        struct hwrng rng;
};

static int ingenic_rng_init(struct hwrng *rng)
{
        struct ingenic_rng *priv = container_of(rng, struct ingenic_rng, rng);

        writel(ERNG_ENABLE, priv->base + RNG_REG_ERNG_OFFSET);

        return 0;
}

static void ingenic_rng_cleanup(struct hwrng *rng)
{
        struct ingenic_rng *priv = container_of(rng, struct ingenic_rng, rng);

        writel(0, priv->base + RNG_REG_ERNG_OFFSET);
}

static int ingenic_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
        struct ingenic_rng *priv = container_of(rng, struct ingenic_rng, rng);
        u32 *data = buf;
        u32 status;
        int ret;

        if (priv->version >= ID_X1000) {
                ret = readl_poll_timeout(priv->base + RNG_REG_ERNG_OFFSET, status,
                                         status & ERNG_READY, 10, 1000);
                if (ret == -ETIMEDOUT) {
                        pr_err("%s: Wait for RNG data ready timeout\n", __func__);
                        return ret;
                }
        } else {
                /*
                 * A delay is required so that the current RNG data is not bit shifted
                 * version of previous RNG data which could happen if random data is
                 * read continuously from this device.
                 */
                udelay(20);
        }

        *data = readl(priv->base + RNG_REG_RNG_OFFSET);

        return 4;
}

static int ingenic_rng_probe(struct platform_device *pdev)
{
        struct ingenic_rng *priv;
        int ret;

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

        priv->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(priv->base)) {
                pr_err("%s: Failed to map RNG registers\n", __func__);
                return PTR_ERR(priv->base);
        }

        priv->version = (enum ingenic_rng_version)(uintptr_t)of_device_get_match_data(&pdev->dev);

        priv->rng.name = pdev->name;
        priv->rng.init = ingenic_rng_init;
        priv->rng.cleanup = ingenic_rng_cleanup;
        priv->rng.read = ingenic_rng_read;

        ret = hwrng_register(&priv->rng);
        if (ret) {
                dev_err(&pdev->dev, "Failed to register hwrng\n");
                return ret;
        }

        platform_set_drvdata(pdev, priv);

        dev_info(&pdev->dev, "Ingenic RNG driver registered\n");
        return 0;
}

static void ingenic_rng_remove(struct platform_device *pdev)
{
        struct ingenic_rng *priv = platform_get_drvdata(pdev);

        hwrng_unregister(&priv->rng);

        writel(0, priv->base + RNG_REG_ERNG_OFFSET);
}

static const struct of_device_id ingenic_rng_of_match[] = {
        { .compatible = "ingenic,jz4780-rng", .data = (void *) ID_JZ4780 },
        { .compatible = "ingenic,x1000-rng", .data = (void *) ID_X1000 },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ingenic_rng_of_match);

static struct platform_driver ingenic_rng_driver = {
        .probe          = ingenic_rng_probe,
        .remove         = ingenic_rng_remove,
        .driver         = {
                .name   = "ingenic-rng",
                .of_match_table = ingenic_rng_of_match,
        },
};

module_platform_driver(ingenic_rng_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>");
MODULE_AUTHOR("周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>");
MODULE_DESCRIPTION("Ingenic Random Number Generator driver");