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 
16 static 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 
32 static struct hwrng powernv_hwrng = {
33 	.name = "powernv-rng",
34 	.read = powernv_rng_read,
35 };
36 
37 static 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 
55 static const struct of_device_id powernv_rng_match[] = {
56 	{ .compatible	= "ibm,power-rng",},
57 	{},
58 };
59 MODULE_DEVICE_TABLE(of, powernv_rng_match);
60 
61 static 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 };
68 module_platform_driver(powernv_rng_driver);
69 
70 MODULE_LICENSE("GPL");
71 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
72