// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * RNG driver for Freescale RNGA
 *
 * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
 * Author: Alan Carvalho de Assis <acassis@gmail.com>
 */

/*
 *
 * This driver is based on other RNG drivers.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>

/* RNGA Registers */
#define RNGA_CONTROL                    0x00
#define RNGA_STATUS                     0x04
#define RNGA_ENTROPY                    0x08
#define RNGA_OUTPUT_FIFO                0x0c
#define RNGA_MODE                       0x10
#define RNGA_VERIFICATION_CONTROL       0x14
#define RNGA_OSC_CONTROL_COUNTER        0x18
#define RNGA_OSC1_COUNTER               0x1c
#define RNGA_OSC2_COUNTER               0x20
#define RNGA_OSC_COUNTER_STATUS         0x24

/* RNGA Registers Range */
#define RNG_ADDR_RANGE                  0x28

/* RNGA Control Register */
#define RNGA_CONTROL_SLEEP              0x00000010
#define RNGA_CONTROL_CLEAR_INT          0x00000008
#define RNGA_CONTROL_MASK_INTS          0x00000004
#define RNGA_CONTROL_HIGH_ASSURANCE     0x00000002
#define RNGA_CONTROL_GO                 0x00000001

#define RNGA_STATUS_LEVEL_MASK          0x0000ff00

/* RNGA Status Register */
#define RNGA_STATUS_OSC_DEAD            0x80000000
#define RNGA_STATUS_SLEEP               0x00000010
#define RNGA_STATUS_ERROR_INT           0x00000008
#define RNGA_STATUS_FIFO_UNDERFLOW      0x00000004
#define RNGA_STATUS_LAST_READ_STATUS    0x00000002
#define RNGA_STATUS_SECURITY_VIOLATION  0x00000001

struct mxc_rng {
        struct device *dev;
        struct hwrng rng;
        void __iomem *mem;
        struct clk *clk;
};

static int mxc_rnga_data_present(struct hwrng *rng, int wait)
{
        int i;
        struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);

        for (i = 0; i < 20; i++) {
                /* how many random numbers are in FIFO? [0-16] */
                int level = (__raw_readl(mxc_rng->mem + RNGA_STATUS) &
                                RNGA_STATUS_LEVEL_MASK) >> 8;
                if (level || !wait)
                        return !!level;
                udelay(10);
        }
        return 0;
}

static int mxc_rnga_data_read(struct hwrng *rng, u32 * data)
{
        int err;
        u32 ctrl;
        struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);

        /* retrieve a random number from FIFO */
        *data = __raw_readl(mxc_rng->mem + RNGA_OUTPUT_FIFO);

        /* some error while reading this random number? */
        err = __raw_readl(mxc_rng->mem + RNGA_STATUS) & RNGA_STATUS_ERROR_INT;

        /* if error: clear error interrupt, but doesn't return random number */
        if (err) {
                dev_dbg(mxc_rng->dev, "Error while reading random number!\n");
                ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
                __raw_writel(ctrl | RNGA_CONTROL_CLEAR_INT,
                                        mxc_rng->mem + RNGA_CONTROL);
                return 0;
        } else
                return 4;
}

static int mxc_rnga_init(struct hwrng *rng)
{
        u32 ctrl, osc;
        struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);

        /* wake up */
        ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
        __raw_writel(ctrl & ~RNGA_CONTROL_SLEEP, mxc_rng->mem + RNGA_CONTROL);

        /* verify if oscillator is working */
        osc = __raw_readl(mxc_rng->mem + RNGA_STATUS);
        if (osc & RNGA_STATUS_OSC_DEAD) {
                dev_err(mxc_rng->dev, "RNGA Oscillator is dead!\n");
                return -ENODEV;
        }

        /* go running */
        ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
        __raw_writel(ctrl | RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);

        return 0;
}

static void mxc_rnga_cleanup(struct hwrng *rng)
{
        u32 ctrl;
        struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);

        ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);

        /* stop rnga */
        __raw_writel(ctrl & ~RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
}

static int mxc_rnga_probe(struct platform_device *pdev)
{
        int err;
        struct mxc_rng *mxc_rng;

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

        mxc_rng->dev = &pdev->dev;
        mxc_rng->rng.name = "mxc-rnga";
        mxc_rng->rng.init = mxc_rnga_init;
        mxc_rng->rng.cleanup = mxc_rnga_cleanup;
        mxc_rng->rng.data_present = mxc_rnga_data_present;
        mxc_rng->rng.data_read = mxc_rnga_data_read;

        mxc_rng->clk = devm_clk_get_enabled(&pdev->dev, NULL);
        if (IS_ERR(mxc_rng->clk)) {
                dev_err(&pdev->dev, "Could not get rng_clk!\n");
                return PTR_ERR(mxc_rng->clk);
        }

        mxc_rng->mem = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(mxc_rng->mem)) {
                err = PTR_ERR(mxc_rng->mem);
                return err;
        }

        err = hwrng_register(&mxc_rng->rng);
        if (err) {
                dev_err(&pdev->dev, "MXC RNGA registering failed (%d)\n", err);
                return err;
        }

        return 0;
}

static void mxc_rnga_remove(struct platform_device *pdev)
{
        struct mxc_rng *mxc_rng = platform_get_drvdata(pdev);

        hwrng_unregister(&mxc_rng->rng);
}

static const struct of_device_id mxc_rnga_of_match[] = {
        { .compatible = "fsl,imx21-rnga", },
        { .compatible = "fsl,imx31-rnga", },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, mxc_rnga_of_match);

static struct platform_driver mxc_rnga_driver = {
        .driver = {
                .name = "mxc_rnga",
                .of_match_table = mxc_rnga_of_match,
        },
        .probe = mxc_rnga_probe,
        .remove = mxc_rnga_remove,
};

module_platform_driver(mxc_rnga_driver);

MODULE_AUTHOR("Freescale Semiconductor, Inc.");
MODULE_DESCRIPTION("H/W RNGA driver for i.MX");
MODULE_LICENSE("GPL");