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
bcm2835_rng_read(struct hwrng * rng,void * buf,size_t max,bool wait)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
bcm2835_rng_probe(struct platform_device * pdev)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
bcm2835_rng_remove(struct platform_device * pdev)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("GPLv2");
114