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