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 
28 static 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  */
54 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
55 {
56 	return 0;
57 };
58 
59 static struct hwrng pseries_rng = {
60 	.name		= KBUILD_MODNAME,
61 	.read		= pseries_rng_read,
62 };
63 
64 static int pseries_rng_probe(struct vio_dev *dev,
65 		const struct vio_device_id *id)
66 {
67 	return hwrng_register(&pseries_rng);
68 }
69 
70 static int pseries_rng_remove(struct vio_dev *dev)
71 {
72 	hwrng_unregister(&pseries_rng);
73 	return 0;
74 }
75 
76 static struct vio_device_id pseries_rng_driver_ids[] = {
77 	{ "ibm,random-v1", "ibm,random"},
78 	{ "", "" }
79 };
80 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
81 
82 static 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 
90 static 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 
96 module_init(rng_init);
97 
98 static void __exit rng_exit(void)
99 {
100 	vio_unregister_driver(&pseries_rng_driver);
101 }
102 module_exit(rng_exit);
103 
104 MODULE_LICENSE("GPL");
105 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
106 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
107