1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
 4 */
 5
 6#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
 7
 8#include <linux/module.h>
 9#include <linux/mod_devicetable.h>
10#include <linux/kernel.h>
11#include <linux/platform_device.h>
12#include <linux/random.h>
13#include <linux/hw_random.h>
14
15static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
16{
17	unsigned long *buf;
18	int i, len;
19
20	/* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
21	len = max / sizeof(unsigned long);
22
23	buf = (unsigned long *)data;
24
25	for (i = 0; i < len; i++)
26		powernv_get_random_long(buf++);
27
28	return len * sizeof(unsigned long);
29}
30
31static struct hwrng powernv_hwrng = {
32	.name = "powernv-rng",
33	.read = powernv_rng_read,
34};
35
36static int powernv_rng_probe(struct platform_device *pdev)
37{
38	int rc;
39
40	rc = devm_hwrng_register(&pdev->dev, &powernv_hwrng);
41	if (rc) {
42		/* We only register one device, ignore any others */
43		if (rc == -EEXIST)
44			rc = -ENODEV;
45
46		return rc;
47	}
48
49	pr_info("Registered powernv hwrng.\n");
50
51	return 0;
52}
53
54static const struct of_device_id powernv_rng_match[] = {
55	{ .compatible	= "ibm,power-rng",},
56	{},
57};
58MODULE_DEVICE_TABLE(of, powernv_rng_match);
59
60static struct platform_driver powernv_rng_driver = {
61	.driver = {
62		.name = "powernv_rng",
63		.of_match_table = powernv_rng_match,
64	},
65	.probe	= powernv_rng_probe,
66};
67module_platform_driver(powernv_rng_driver);
68
69MODULE_LICENSE("GPL");
70MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");