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/mod_devicetable.h>
14 #include <linux/kernel.h>
15 #include <linux/platform_device.h>
16 #include <linux/random.h>
17 #include <linux/hw_random.h>
18
powernv_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)19 static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
20 {
21 unsigned long *buf;
22 int i, len;
23
24 /* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
25 len = max / sizeof(unsigned long);
26
27 buf = (unsigned long *)data;
28
29 for (i = 0; i < len; i++)
30 powernv_get_random_long(buf++);
31
32 return len * sizeof(unsigned long);
33 }
34
35 static struct hwrng powernv_hwrng = {
36 .name = "powernv-rng",
37 .read = powernv_rng_read,
38 };
39
powernv_rng_remove(struct platform_device * pdev)40 static int powernv_rng_remove(struct platform_device *pdev)
41 {
42 hwrng_unregister(&powernv_hwrng);
43
44 return 0;
45 }
46
powernv_rng_probe(struct platform_device * pdev)47 static int powernv_rng_probe(struct platform_device *pdev)
48 {
49 int rc;
50
51 rc = hwrng_register(&powernv_hwrng);
52 if (rc) {
53 /* We only register one device, ignore any others */
54 if (rc == -EEXIST)
55 rc = -ENODEV;
56
57 return rc;
58 }
59
60 pr_info("Registered powernv hwrng.\n");
61
62 return 0;
63 }
64
65 static const struct of_device_id powernv_rng_match[] = {
66 { .compatible = "ibm,power-rng",},
67 {},
68 };
69 MODULE_DEVICE_TABLE(of, powernv_rng_match);
70
71 static struct platform_driver powernv_rng_driver = {
72 .driver = {
73 .name = "powernv_rng",
74 .of_match_table = powernv_rng_match,
75 },
76 .probe = powernv_rng_probe,
77 .remove = powernv_rng_remove,
78 };
79 module_platform_driver(powernv_rng_driver);
80
81 MODULE_LICENSE("GPL");
82 MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");
83
