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 
15 static 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 
31 static struct hwrng powernv_hwrng = {
32 	.name = "powernv-rng",
33 	.read = powernv_rng_read,
34 };
35 
36 static 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 
54 static const struct of_device_id powernv_rng_match[] = {
55 	{ .compatible	= "ibm,power-rng",},
56 	{},
57 };
58 MODULE_DEVICE_TABLE(of, powernv_rng_match);
59 
60 static 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 };
67 module_platform_driver(powernv_rng_driver);
68 
69 MODULE_LICENSE("GPL");
70 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
71