1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2010 Michael Neuling IBM Corporation
4 *
5 * Driver for the pseries hardware RNG for POWER7+ and above
6 */
7
8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/hw_random.h>
13#include <asm/vio.h>
14
15
16static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
17{
18	u64 buffer[PLPAR_HCALL_BUFSIZE];
19	int rc;
20
21	rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
22	if (rc != H_SUCCESS) {
23		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
24		return -EIO;
25	}
26	memcpy(data, buffer, 8);
27
28	/* The hypervisor interface returns 64 bits */
29	return 8;
30}
31
32/*
33 * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
34 *
35 * This is a required function for a driver to operate in a CMO environment
36 * but this device does not make use of DMA allocations, return 0.
37 *
38 * Return value:
39 *	Number of bytes of IO data the driver will need to perform well -> 0
40 */
41static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
42{
43	return 0;
44};
45
46static struct hwrng pseries_rng = {
47	.name		= KBUILD_MODNAME,
48	.read		= pseries_rng_read,
49};
50
51static int pseries_rng_probe(struct vio_dev *dev,
52		const struct vio_device_id *id)
53{
54	return hwrng_register(&pseries_rng);
55}
56
57static void pseries_rng_remove(struct vio_dev *dev)
58{
59	hwrng_unregister(&pseries_rng);
60}
61
62static const struct vio_device_id pseries_rng_driver_ids[] = {
63	{ "ibm,random-v1", "ibm,random"},
64	{ "", "" }
65};
66MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
67
68static struct vio_driver pseries_rng_driver = {
69	.name = KBUILD_MODNAME,
70	.probe = pseries_rng_probe,
71	.remove = pseries_rng_remove,
72	.get_desired_dma = pseries_rng_get_desired_dma,
73	.id_table = pseries_rng_driver_ids
74};
75
76static int __init rng_init(void)
77{
78	pr_info("Registering IBM pSeries RNG driver\n");
79	return vio_register_driver(&pseries_rng_driver);
80}
81
82module_init(rng_init);
83
84static void __exit rng_exit(void)
85{
86	vio_unregister_driver(&pseries_rng_driver);
87}
88module_exit(rng_exit);
89
90MODULE_LICENSE("GPL");
91MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
92MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
93