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/init.h>
12 #include <linux/io.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/of_address.h>
16 #include <linux/of_platform.h>
17 #include <linux/platform_device.h>
18 #include <linux/printk.h>
19 
20 #define RNG_CTRL	0x0
21 #define RNG_STATUS	0x4
22 #define RNG_DATA	0x8
23 
24 /* enable rng */
25 #define RNG_RBGEN	0x1
26 
27 /* the initial numbers generated are "less random" so will be discarded */
28 #define RNG_WARMUP_COUNT 0x40000
29 
30 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
31 			       bool wait)
32 {
33 	void __iomem *rng_base = (void __iomem *)rng->priv;
34 
35 	while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
36 		if (!wait)
37 			return 0;
38 		cpu_relax();
39 	}
40 
41 	*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
42 	return sizeof(u32);
43 }
44 
45 static struct hwrng bcm2835_rng_ops = {
46 	.name	= "bcm2835",
47 	.read	= bcm2835_rng_read,
48 };
49 
50 static int bcm2835_rng_probe(struct platform_device *pdev)
51 {
52 	struct device *dev = &pdev->dev;
53 	struct device_node *np = dev->of_node;
54 	void __iomem *rng_base;
55 	int err;
56 
57 	/* map peripheral */
58 	rng_base = of_iomap(np, 0);
59 	if (!rng_base) {
60 		dev_err(dev, "failed to remap rng regs");
61 		return -ENODEV;
62 	}
63 	bcm2835_rng_ops.priv = (unsigned long)rng_base;
64 
65 	/* register driver */
66 	err = hwrng_register(&bcm2835_rng_ops);
67 	if (err) {
68 		dev_err(dev, "hwrng registration failed\n");
69 		iounmap(rng_base);
70 	} else {
71 		dev_info(dev, "hwrng registered\n");
72 
73 		/* set warm-up count & enable */
74 		__raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
75 		__raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
76 	}
77 	return err;
78 }
79 
80 static int bcm2835_rng_remove(struct platform_device *pdev)
81 {
82 	void __iomem *rng_base = (void __iomem *)bcm2835_rng_ops.priv;
83 
84 	/* disable rng hardware */
85 	__raw_writel(0, rng_base + RNG_CTRL);
86 
87 	/* unregister driver */
88 	hwrng_unregister(&bcm2835_rng_ops);
89 	iounmap(rng_base);
90 
91 	return 0;
92 }
93 
94 static const struct of_device_id bcm2835_rng_of_match[] = {
95 	{ .compatible = "brcm,bcm2835-rng", },
96 	{},
97 };
98 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
99 
100 static struct platform_driver bcm2835_rng_driver = {
101 	.driver = {
102 		.name = "bcm2835-rng",
103 		.owner = THIS_MODULE,
104 		.of_match_table = bcm2835_rng_of_match,
105 	},
106 	.probe		= bcm2835_rng_probe,
107 	.remove		= bcm2835_rng_remove,
108 };
109 module_platform_driver(bcm2835_rng_driver);
110 
111 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
112 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
113 MODULE_LICENSE("GPL v2");
114