1/*
2 * Copyright (C) 2010 Michael Neuling IBM Corporation
3 *
4 * Driver for the pseries hardware RNG for POWER7+ and above
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
18 */
19
20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/hw_random.h>
25#include <asm/vio.h>
26
27
28static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
29{
30	u64 buffer[PLPAR_HCALL_BUFSIZE];
31	size_t size = max < 8 ? max : 8;
32	int rc;
33
34	rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
35	if (rc != H_SUCCESS) {
36		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
37		return -EIO;
38	}
39	memcpy(data, buffer, size);
40
41	/* The hypervisor interface returns 64 bits */
42	return size;
43}
44
45/**
46 * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
47 *
48 * This is a required function for a driver to operate in a CMO environment
49 * but this device does not make use of DMA allocations, return 0.
50 *
51 * Return value:
52 *	Number of bytes of IO data the driver will need to perform well -> 0
53 */
54static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
55{
56	return 0;
57};
58
59static struct hwrng pseries_rng = {
60	.name		= KBUILD_MODNAME,
61	.read		= pseries_rng_read,
62};
63
64static int pseries_rng_probe(struct vio_dev *dev,
65		const struct vio_device_id *id)
66{
67	return hwrng_register(&pseries_rng);
68}
69
70static int pseries_rng_remove(struct vio_dev *dev)
71{
72	hwrng_unregister(&pseries_rng);
73	return 0;
74}
75
76static struct vio_device_id pseries_rng_driver_ids[] = {
77	{ "ibm,random-v1", "ibm,random"},
78	{ "", "" }
79};
80MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
81
82static struct vio_driver pseries_rng_driver = {
83	.name = KBUILD_MODNAME,
84	.probe = pseries_rng_probe,
85	.remove = pseries_rng_remove,
86	.get_desired_dma = pseries_rng_get_desired_dma,
87	.id_table = pseries_rng_driver_ids
88};
89
90static int __init rng_init(void)
91{
92	pr_info("Registering IBM pSeries RNG driver\n");
93	return vio_register_driver(&pseries_rng_driver);
94}
95
96module_init(rng_init);
97
98static void __exit rng_exit(void)
99{
100	vio_unregister_driver(&pseries_rng_driver);
101}
102module_exit(rng_exit);
103
104MODULE_LICENSE("GPL");
105MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
106MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
107