1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2010 Michael Neuling IBM Corporation
4  *
5  * Driver for the pseries hardware RNG for POWER7+ and above
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/hw_random.h>
13 #include <asm/vio.h>
14 
15 
16 static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
17 {
18 	u64 buffer[PLPAR_HCALL_BUFSIZE];
19 	int rc;
20 
21 	rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
22 	if (rc != H_SUCCESS) {
23 		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
24 		return -EIO;
25 	}
26 	memcpy(data, buffer, 8);
27 
28 	/* The hypervisor interface returns 64 bits */
29 	return 8;
30 }
31 
32 /**
33  * pseries_rng_get_desired_dma - Return desired DMA allocate for CMO operations
34  *
35  * This is a required function for a driver to operate in a CMO environment
36  * but this device does not make use of DMA allocations, return 0.
37  *
38  * Return value:
39  *	Number of bytes of IO data the driver will need to perform well -> 0
40  */
41 static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
42 {
43 	return 0;
44 };
45 
46 static struct hwrng pseries_rng = {
47 	.name		= KBUILD_MODNAME,
48 	.read		= pseries_rng_read,
49 };
50 
51 static int pseries_rng_probe(struct vio_dev *dev,
52 		const struct vio_device_id *id)
53 {
54 	return hwrng_register(&pseries_rng);
55 }
56 
57 static void pseries_rng_remove(struct vio_dev *dev)
58 {
59 	hwrng_unregister(&pseries_rng);
60 }
61 
62 static const struct vio_device_id pseries_rng_driver_ids[] = {
63 	{ "ibm,random-v1", "ibm,random"},
64 	{ "", "" }
65 };
66 MODULE_DEVICE_TABLE(vio, pseries_rng_driver_ids);
67 
68 static struct vio_driver pseries_rng_driver = {
69 	.name = KBUILD_MODNAME,
70 	.probe = pseries_rng_probe,
71 	.remove = pseries_rng_remove,
72 	.get_desired_dma = pseries_rng_get_desired_dma,
73 	.id_table = pseries_rng_driver_ids
74 };
75 
76 static int __init rng_init(void)
77 {
78 	pr_info("Registering IBM pSeries RNG driver\n");
79 	return vio_register_driver(&pseries_rng_driver);
80 }
81 
82 module_init(rng_init);
83 
84 static void __exit rng_exit(void)
85 {
86 	vio_unregister_driver(&pseries_rng_driver);
87 }
88 module_exit(rng_exit);
89 
90 MODULE_LICENSE("GPL");
91 MODULE_AUTHOR("Michael Neuling <mikey@neuling.org>");
92 MODULE_DESCRIPTION("H/W RNG driver for IBM pSeries processors");
93