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
powernv_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)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
powernv_rng_probe(struct platform_device * pdev)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