bcm2835-rng.c
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/**
* Copyright (c) 2010-2012 Broadcom. All rights reserved.
* Copyright (c) 2013 Lubomir Rintel
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License ("GPL")
* version 2, as published by the Free Software Foundation.
*/
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/printk.h>
#define RNG_CTRL 0x0
#define RNG_STATUS 0x4
#define RNG_DATA 0x8
/* enable rng */
#define RNG_RBGEN 0x1
/* the initial numbers generated are "less random" so will be discarded */
#define RNG_WARMUP_COUNT 0x40000
static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
bool wait)
{
void __iomem *rng_base = (void __iomem *)rng->priv;
while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
if (!wait)
return 0;
cpu_relax();
}
*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
return sizeof(u32);
}
static struct hwrng bcm2835_rng_ops = {
.name = "bcm2835",
.read = bcm2835_rng_read,
};
static int bcm2835_rng_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct device_node *np = dev->of_node;
void __iomem *rng_base;
int err;
/* map peripheral */
rng_base = of_iomap(np, 0);
if (!rng_base) {
dev_err(dev, "failed to remap rng regs");
return -ENODEV;
}
bcm2835_rng_ops.priv = (unsigned long)rng_base;
/* set warm-up count & enable */
__raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
__raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
/* register driver */
err = hwrng_register(&bcm2835_rng_ops);
if (err) {
dev_err(dev, "hwrng registration failed\n");
iounmap(rng_base);
} else
dev_info(dev, "hwrng registered\n");
return err;
}
static int bcm2835_rng_remove(struct platform_device *pdev)
{
void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
/* disable rng hardware */
__raw_writel(0, rng_base + RNG_CTRL);
/* unregister driver */
hwrng_unregister(&bcm2835_rng_ops);
iounmap(rng_base);
return 0;
}
static const struct of_device_id bcm2835_rng_of_match[] = {
{ .compatible = "brcm,bcm2835-rng", },
{},
};
MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
static struct platform_driver bcm2835_rng_driver = {
.driver = {
.name = "bcm2835-rng",
.of_match_table = bcm2835_rng_of_match,
},
.probe = bcm2835_rng_probe,
.remove = bcm2835_rng_remove,
};
module_platform_driver(bcm2835_rng_driver);
MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL v2");