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/*
 * RNG driver for Moschip MCS814x SoC
 *
 * Copyright 2012 (C), Florian Fainelli <florian@openwrt.org>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

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

#define STAT    0x00
#define RND     0x04

struct mcs814x_rng_priv {
        void __iomem    *regs;
};

static int mcs814x_rng_data_read(struct hwrng *rng, u32 *buffer)
{
        struct mcs814x_rng_priv *priv = (struct mcs814x_rng_priv *)rng->priv;

        *buffer = readl_relaxed(priv->regs + RND);

        return 4;
}

static int mcs814x_rng_probe(struct platform_device *pdev)
{
        struct resource *res;
        struct mcs814x_rng_priv *priv;
        struct hwrng *rng;
        int ret;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv) {
                ret = -ENOMEM;
                goto out;
        }

        rng = kzalloc(sizeof(*rng), GFP_KERNEL);
        if (!rng) {
                ret = -ENOMEM;
                goto out_priv;
        }

        platform_set_drvdata(pdev, rng);
        rng->priv = (unsigned long)priv;
        rng->name = pdev->name;
        rng->data_read = mcs814x_rng_data_read;

        priv->regs = devm_ioremap_resource(&pdev->dev, res);
        if (!priv->regs) {
                ret = -ENOMEM;
                goto out_rng;
        }

        ret = hwrng_register(rng);
        if (ret) {
                dev_err(&pdev->dev, "failed to register hwrng driver\n");
                goto out;
        }

        dev_info(&pdev->dev, "registered\n");

        return ret;

out_rng:
        platform_set_drvdata(pdev, NULL);
        kfree(rng);
out_priv:
        kfree(priv);
out:
        return ret;
}

static int mcs814x_rng_remove(struct platform_device *pdev)
{
        struct hwrng *rng = platform_get_drvdata(pdev);
        struct mcs814x_rng_priv *priv = (struct mcs814x_rng_priv *)rng->priv;

        hwrng_unregister(rng);
        kfree(priv);
        kfree(rng);
        platform_set_drvdata(pdev, NULL);

        return 0;
}

static const struct of_device_id mcs814x_rng_ids[] = {
        { .compatible = "moschip,mcs814x-rng", },
        { /* sentinel */ },
};

static struct platform_driver mcs814x_rng_driver = {
        .driver = {
                .name   = "mcs814x-rng",
                .owner  = THIS_MODULE,
                .of_match_table = mcs814x_rng_ids,
        },
        .probe  = mcs814x_rng_probe,
        .remove = mcs814x_rng_remove,
};

module_platform_driver(mcs814x_rng_driver);

MODULE_AUTHOR("Florian Fainelli <florian@openwrt.org>");
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) for Moschip MCS814x");
MODULE_LICENSE("GPL");