1/**
  2 * Copyright (c) 2010-2012 Broadcom. All rights reserved.
  3 * Copyright (c) 2013 Lubomir Rintel
  4 *
  5 * This program is free software; you can redistribute it and/or
  6 * modify it under the terms of the GNU General Public License ("GPL")
  7 * version 2, as published by the Free Software Foundation.
  8 */
  9
 10#include <linux/hw_random.h>
 11#include <linux/io.h>
 12#include <linux/kernel.h>
 13#include <linux/module.h>
 14#include <linux/of_address.h>
 15#include <linux/of_platform.h>
 16#include <linux/platform_device.h>
 17#include <linux/printk.h>
 18
 19#define RNG_CTRL	0x0
 20#define RNG_STATUS	0x4
 21#define RNG_DATA	0x8
 22
 23/* enable rng */
 24#define RNG_RBGEN	0x1
 25
 26/* the initial numbers generated are "less random" so will be discarded */
 27#define RNG_WARMUP_COUNT 0x40000
 28
 29static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
 30			       bool wait)
 31{
 32	void __iomem *rng_base = (void __iomem *)rng->priv;
 33
 34	while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
 35		if (!wait)
 36			return 0;
 37		cpu_relax();
 38	}
 39
 40	*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
 41	return sizeof(u32);
 42}
 43
 44static struct hwrng bcm2835_rng_ops = {
 45	.name	= "bcm2835",
 46	.read	= bcm2835_rng_read,
 47};
 48
 49static int bcm2835_rng_probe(struct platform_device *pdev)
 50{
 51	struct device *dev = &pdev->dev;
 52	struct device_node *np = dev->of_node;
 53	void __iomem *rng_base;
 54	int err;
 55
 56	/* map peripheral */
 57	rng_base = of_iomap(np, 0);
 58	if (!rng_base) {
 59		dev_err(dev, "failed to remap rng regs");
 60		return -ENODEV;
 61	}
 62	bcm2835_rng_ops.priv = (unsigned long)rng_base;
 63
 64	/* set warm-up count & enable */
 65	__raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
 66	__raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
 67
 68	/* register driver */
 69	err = hwrng_register(&bcm2835_rng_ops);
 70	if (err) {
 71		dev_err(dev, "hwrng registration failed\n");
 72		iounmap(rng_base);
 73	} else
 74		dev_info(dev, "hwrng registered\n");
 75
 76	return err;
 77}
 78
 79static int bcm2835_rng_remove(struct platform_device *pdev)
 80{
 81	void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
 82
 83	/* disable rng hardware */
 84	__raw_writel(0, rng_base + RNG_CTRL);
 85
 86	/* unregister driver */
 87	hwrng_unregister(&bcm2835_rng_ops);
 88	iounmap(rng_base);
 89
 90	return 0;
 91}
 92
 93static const struct of_device_id bcm2835_rng_of_match[] = {
 94	{ .compatible = "brcm,bcm2835-rng", },
 95	{},
 96};
 97MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
 98
 99static struct platform_driver bcm2835_rng_driver = {
100	.driver = {
101		.name = "bcm2835-rng",
102		.owner = THIS_MODULE,
103		.of_match_table = bcm2835_rng_of_match,
104	},
105	.probe		= bcm2835_rng_probe,
106	.remove		= bcm2835_rng_remove,
107};
108module_platform_driver(bcm2835_rng_driver);
109
110MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
111MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
112MODULE_LICENSE("GPL v2");