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		.of_match_table = bcm2835_rng_of_match,
103	},
104	.probe		= bcm2835_rng_probe,
105	.remove		= bcm2835_rng_remove,
106};
107module_platform_driver(bcm2835_rng_driver);
108
109MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
110MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
111MODULE_LICENSE("GPL v2");
112