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#include <asm/archrandom.h>
15
16static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
17{
18	unsigned long *buf;
19	int i, len;
20
21	/* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
22	len = max / sizeof(unsigned long);
23
24	buf = (unsigned long *)data;
25
26	for (i = 0; i < len; i++)
27		pnv_get_random_long(buf++);
28
29	return len * sizeof(unsigned long);
30}
31
32static struct hwrng powernv_hwrng = {
33	.name = "powernv-rng",
34	.read = powernv_rng_read,
35};
36
37static int powernv_rng_probe(struct platform_device *pdev)
38{
39	int rc;
40
41	rc = devm_hwrng_register(&pdev->dev, &powernv_hwrng);
42	if (rc) {
43		/* We only register one device, ignore any others */
44		if (rc == -EEXIST)
45			rc = -ENODEV;
46
47		return rc;
48	}
49
50	pr_info("Registered powernv hwrng.\n");
51
52	return 0;
53}
54
55static const struct of_device_id powernv_rng_match[] = {
56	{ .compatible	= "ibm,power-rng",},
57	{},
58};
59MODULE_DEVICE_TABLE(of, powernv_rng_match);
60
61static struct platform_driver powernv_rng_driver = {
62	.driver = {
63		.name = "powernv_rng",
64		.of_match_table = powernv_rng_match,
65	},
66	.probe	= powernv_rng_probe,
67};
68module_platform_driver(powernv_rng_driver);
69
70MODULE_LICENSE("GPL");
71MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
72