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
18static 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
34static struct hwrng powernv_hwrng = {
35	.name = "powernv-rng",
36	.read = powernv_rng_read,
37};
38
39static int powernv_rng_remove(struct platform_device *pdev)
40{
41	hwrng_unregister(&powernv_hwrng);
42
43	return 0;
44}
45
46static 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
64static const struct of_device_id powernv_rng_match[] = {
65	{ .compatible	= "ibm,power-rng",},
66	{},
67};
68MODULE_DEVICE_TABLE(of, powernv_rng_match);
69
70static 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};
78module_platform_driver(powernv_rng_driver);
79
80MODULE_LICENSE("GPL");
81MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
82