1 /*
2  * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation; either version
7  * 2 of the License, or (at your option) any later version.
8  */
9 
10 #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
11 
12 #include <linux/module.h>
13 #include <linux/kernel.h>
14 #include <linux/platform_device.h>
15 #include <linux/random.h>
16 #include <linux/hw_random.h>
17 
18 static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
19 {
20 	unsigned long *buf;
21 	int i, len;
22 
23 	/* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
24 	len = max / sizeof(unsigned long);
25 
26 	buf = (unsigned long *)data;
27 
28 	for (i = 0; i < len; i++)
29 		powernv_get_random_long(buf++);
30 
31 	return len * sizeof(unsigned long);
32 }
33 
34 static struct hwrng powernv_hwrng = {
35 	.name = "powernv-rng",
36 	.read = powernv_rng_read,
37 };
38 
39 static int powernv_rng_remove(struct platform_device *pdev)
40 {
41 	hwrng_unregister(&powernv_hwrng);
42 
43 	return 0;
44 }
45 
46 static int powernv_rng_probe(struct platform_device *pdev)
47 {
48 	int rc;
49 
50 	rc = hwrng_register(&powernv_hwrng);
51 	if (rc) {
52 		/* We only register one device, ignore any others */
53 		if (rc == -EEXIST)
54 			rc = -ENODEV;
55 
56 		return rc;
57 	}
58 
59 	pr_info("Registered powernv hwrng.\n");
60 
61 	return 0;
62 }
63 
64 static const struct of_device_id powernv_rng_match[] = {
65 	{ .compatible	= "ibm,power-rng",},
66 	{},
67 };
68 MODULE_DEVICE_TABLE(of, powernv_rng_match);
69 
70 static struct platform_driver powernv_rng_driver = {
71 	.driver = {
72 		.name = "powernv_rng",
73 		.of_match_table = powernv_rng_match,
74 	},
75 	.probe	= powernv_rng_probe,
76 	.remove = powernv_rng_remove,
77 };
78 module_platform_driver(powernv_rng_driver);
79 
80 MODULE_LICENSE("GPL");
81 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
82