mxc-rnga.c

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/*
 * RNG driver for Freescale RNGA
 *
 * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
 * Author: Alan Carvalho de Assis <[email protected]>
 */

/*
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 *
 * This driver is based on other RNG drivers.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/delay.h>
#include <linux/io.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 __init mxc_rnga_probe(struct platform_device *pdev)
{
    int err = -ENODEV;
    struct resource *res, *mem;
    struct mxc_rng *mxc_rng;

    mxc_rng = devm_kzalloc(&pdev->dev, sizeof(struct 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(&pdev->dev, NULL);
    if (IS_ERR(mxc_rng->clk)) {
        dev_err(&pdev->dev, "Could not get rng_clk!\n");
        err = PTR_ERR(mxc_rng->clk);
        goto out;
    }

    clk_prepare_enable(mxc_rng->clk);

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res) {
        err = -ENOENT;
        goto err_region;
    }

    mem = request_mem_region(res->start, resource_size(res), pdev->name);
    if (mem == NULL) {
        err = -EBUSY;
        goto err_region;
    }

    mxc_rng->mem = ioremap(res->start, resource_size(res));
    if (!mxc_rng->mem) {
        err = -ENOMEM;
        goto err_ioremap;
    }

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

    dev_info(&pdev->dev, "MXC RNGA Registered.\n");

    return 0;

err_ioremap:
    release_mem_region(res->start, resource_size(res));

err_region:
    clk_disable_unprepare(mxc_rng->clk);

out:
    return err;
}

static int __exit mxc_rnga_remove(struct platform_device *pdev)
{
    struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    struct mxc_rng *mxc_rng = platform_get_drvdata(pdev);

    hwrng_unregister(&mxc_rng->rng);

    iounmap(mxc_rng->mem);

    release_mem_region(res->start, resource_size(res));

    clk_disable_unprepare(mxc_rng->clk);

    return 0;
}

static struct platform_driver mxc_rnga_driver = {
    .driver = {
           .name = "mxc_rnga",
           .owner = THIS_MODULE,
           },
    .remove = __exit_p(mxc_rnga_remove),
};

static int __init mod_init(void)
{
    return platform_driver_probe(&mxc_rnga_driver, mxc_rnga_probe);
}

static void __exit mod_exit(void)
{
    platform_driver_unregister(&mxc_rnga_driver);
}

module_init(mod_init);
module_exit(mod_exit);

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