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/**
* Copyright (c) 2010-2012 Broadcom. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The names of the above-listed copyright holders may not be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* ALTERNATIVELY, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2, as published by the Free
* Software Foundation.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/hw_random.h>
#include <linux/printk.h>

#include <asm/io.h>
#include <mach/hardware.h>
#include <mach/platform.h>

#define RNG_CTRL (0x0)
#define RNG_STATUS (0x4)
#define RNG_DATA (0x8)
#define RNG_FF_THRESHOLD (0xc)

/* enable rng */
#define RNG_RBGEN 0x1
/* double speed, less random mode */
#define RNG_RBG2X 0x2

/* the initial numbers generated are "less random" so will be discarded */
#define RNG_WARMUP_COUNT 0x40000

static int bcm2708_rng_data_read(struct hwrng *rng, u32 *buffer)
{
void __iomem *rng_base = (void __iomem *)rng->priv;
unsigned words;
/* wait for a random number to be in fifo */
        do {
words = __raw_readl(rng_base + RNG_STATUS)>>24;
}
        while (words == 0);
/* read the random number */
*buffer = __raw_readl(rng_base + RNG_DATA);
return 4;
}

static struct hwrng bcm2708_rng_ops = {
.name = "bcm2708",
.data_read = bcm2708_rng_data_read,
};

static int __init bcm2708_rng_init(void)
{
void __iomem *rng_base;
int err;

/* map peripheral */
rng_base = ioremap(RNG_BASE, 0x10);
pr_info("bcm2708_rng_init=%p\n", rng_base);
if (!rng_base) {
pr_err("bcm2708_rng_init failed to ioremap\n");
return -ENOMEM;
}
bcm2708_rng_ops.priv = (unsigned long)rng_base;
/* register driver */
err = hwrng_register(&bcm2708_rng_ops);
if (err) {
pr_err("bcm2708_rng_init hwrng_register()=%d\n", err);
iounmap(rng_base);
} else {
/* set warm-up count & enable */
__raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
__raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
}
return err;
}

static void __exit bcm2708_rng_exit(void)
{
void __iomem *rng_base = (void __iomem *)bcm2708_rng_ops.priv;
pr_info("bcm2708_rng_exit\n");
/* disable rng hardware */
__raw_writel(0, rng_base + RNG_CTRL);
/* unregister driver */
hwrng_unregister(&bcm2708_rng_ops);
iounmap(rng_base);
}

module_init(bcm2708_rng_init);
module_exit(bcm2708_rng_exit);

MODULE_DESCRIPTION("BCM2708 H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL and additional rights");
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