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 #include <linux/module.h>
21 #include <linux/hw_random.h>
22 #include <asm/vio.h>
23 
24 #define MODULE_NAME "pseries-rng"
25 
26 static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
27 {
28 	if (plpar_hcall(H_RANDOM, (unsigned long *)data) != H_SUCCESS) {
29 		printk(KERN_ERR "pseries rng hcall error\n");
30 		return 0;
31 	}
32 	return 8;
33 }
34 
35 /**
36  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
37  *
38  * This is a required function for a driver to operate in a CMO environment
39  * but this device does not make use of DMA allocations, return 0.
40  *
41  * Return value:
42  *	Number of bytes of IO data the driver will need to perform well -> 0
43  */
44 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
45 {
46 	return 0;
47 };
48 
49 static struct hwrng pseries_rng = {
50 	.name		= MODULE_NAME,
51 	.data_read	= pseries_rng_data_read,
52 };
53 
54 static int __init pseries_rng_probe(struct vio_dev *dev,
55 		const struct vio_device_id *id)
56 {
57 	return hwrng_register(&pseries_rng);
58 }
59 
60 static int __exit pseries_rng_remove(struct vio_dev *dev)
61 {
62 	hwrng_unregister(&pseries_rng);
63 	return 0;
64 }
65 
66 static struct vio_device_id pseries_rng_driver_ids[] = {
67 	{ "ibm,random-v1", "ibm,random"},
68 	{ "", "" }
69 };
70 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
71 
72 static struct vio_driver pseries_rng_driver = {
73 	.name = MODULE_NAME,
74 	.probe = pseries_rng_probe,
75 	.remove = pseries_rng_remove,
76 	.get_desired_dma = pseries_rng_get_desired_dma,
77 	.id_table = pseries_rng_driver_ids
78 };
79 
80 static int __init rng_init(void)
81 {
82 	printk(KERN_INFO "Registering IBM pSeries RNG driver\n");
83 	return vio_register_driver(&pseries_rng_driver);
84 }
85 
86 module_init(rng_init);
87 
88 static void __exit rng_exit(void)
89 {
90 	vio_unregister_driver(&pseries_rng_driver);
91 }
92 module_exit(rng_exit);
93 
94 MODULE_LICENSE("GPL");
95 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
96 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
97