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 #define MODULE_NAME "pseries-rng"
28 
29 static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
30 {
31 	int rc;
32 
33 	rc = plpar_hcall(H_RANDOM, (unsigned long *)data);
34 	if (rc != H_SUCCESS) {
35 		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
36 		return -EIO;
37 	}
38 
39 	/* The hypervisor interface returns 64 bits */
40 	return 8;
41 }
42 
43 /**
44  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
45  *
46  * This is a required function for a driver to operate in a CMO environment
47  * but this device does not make use of DMA allocations, return 0.
48  *
49  * Return value:
50  *	Number of bytes of IO data the driver will need to perform well -> 0
51  */
52 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
53 {
54 	return 0;
55 };
56 
57 static struct hwrng pseries_rng = {
58 	.name		= MODULE_NAME,
59 	.data_read	= pseries_rng_data_read,
60 };
61 
62 static int __init pseries_rng_probe(struct vio_dev *dev,
63 		const struct vio_device_id *id)
64 {
65 	return hwrng_register(&pseries_rng);
66 }
67 
68 static int __exit pseries_rng_remove(struct vio_dev *dev)
69 {
70 	hwrng_unregister(&pseries_rng);
71 	return 0;
72 }
73 
74 static struct vio_device_id pseries_rng_driver_ids[] = {
75 	{ "ibm,random-v1", "ibm,random"},
76 	{ "", "" }
77 };
78 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
79 
80 static struct vio_driver pseries_rng_driver = {
81 	.name = MODULE_NAME,
82 	.probe = pseries_rng_probe,
83 	.remove = pseries_rng_remove,
84 	.get_desired_dma = pseries_rng_get_desired_dma,
85 	.id_table = pseries_rng_driver_ids
86 };
87 
88 static int __init rng_init(void)
89 {
90 	printk(KERN_INFO "Registering IBM pSeries RNG driver\n");
91 	return vio_register_driver(&pseries_rng_driver);
92 }
93 
94 module_init(rng_init);
95 
96 static void __exit rng_exit(void)
97 {
98 	vio_unregister_driver(&pseries_rng_driver);
99 }
100 module_exit(rng_exit);
101 
102 MODULE_LICENSE("GPL");
103 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
104 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
105