1 /*
2  * RNG driver for AMD Geode RNGs
3  *
4  * Copyright 2005 (c) MontaVista Software, Inc.
5  *
6  * with the majority of the code coming from:
7  *
8  * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
9  * (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
10  *
11  * derived from
12  *
13  * Hardware driver for the AMD 768 Random Number Generator (RNG)
14  * (c) Copyright 2001 Red Hat Inc
15  *
16  * derived from
17  *
18  * Hardware driver for Intel i810 Random Number Generator (RNG)
19  * Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
20  * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
21  *
22  * This file is licensed under  the terms of the GNU General Public
23  * License version 2. This program is licensed "as is" without any
24  * warranty of any kind, whether express or implied.
25  */
26 
27 #include <linux/module.h>
28 #include <linux/kernel.h>
29 #include <linux/pci.h>
30 #include <linux/hw_random.h>
31 #include <linux/delay.h>
32 #include <asm/io.h>
33 
34 
35 #define PFX	KBUILD_MODNAME ": "
36 
37 #define GEODE_RNG_DATA_REG   0x50
38 #define GEODE_RNG_STATUS_REG 0x54
39 
40 /*
41  * Data for PCI driver interface
42  *
43  * This data only exists for exporting the supported
44  * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
45  * register a pci_driver, because someone else might one day
46  * want to register another driver on the same PCI id.
47  */
48 static const struct pci_device_id pci_tbl[] = {
49 	{ PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_LX_AES), 0, },
50 	{ 0, },	/* terminate list */
51 };
52 MODULE_DEVICE_TABLE(pci, pci_tbl);
53 
54 
55 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
56 {
57 	void __iomem *mem = (void __iomem *)rng->priv;
58 
59 	*data = readl(mem + GEODE_RNG_DATA_REG);
60 
61 	return 4;
62 }
63 
64 static int geode_rng_data_present(struct hwrng *rng, int wait)
65 {
66 	void __iomem *mem = (void __iomem *)rng->priv;
67 	int data, i;
68 
69 	for (i = 0; i < 20; i++) {
70 		data = !!(readl(mem + GEODE_RNG_STATUS_REG));
71 		if (data || !wait)
72 			break;
73 		udelay(10);
74 	}
75 	return data;
76 }
77 
78 
79 static struct hwrng geode_rng = {
80 	.name		= "geode",
81 	.data_present	= geode_rng_data_present,
82 	.data_read	= geode_rng_data_read,
83 };
84 
85 
86 static int __init mod_init(void)
87 {
88 	int err = -ENODEV;
89 	struct pci_dev *pdev = NULL;
90 	const struct pci_device_id *ent;
91 	void __iomem *mem;
92 	unsigned long rng_base;
93 
94 	for_each_pci_dev(pdev) {
95 		ent = pci_match_id(pci_tbl, pdev);
96 		if (ent)
97 			goto found;
98 	}
99 	/* Device not found. */
100 	goto out;
101 
102 found:
103 	rng_base = pci_resource_start(pdev, 0);
104 	if (rng_base == 0)
105 		goto out;
106 	err = -ENOMEM;
107 	mem = ioremap(rng_base, 0x58);
108 	if (!mem)
109 		goto out;
110 	geode_rng.priv = (unsigned long)mem;
111 
112 	pr_info("AMD Geode RNG detected\n");
113 	err = hwrng_register(&geode_rng);
114 	if (err) {
115 		pr_err(PFX "RNG registering failed (%d)\n",
116 		       err);
117 		goto err_unmap;
118 	}
119 out:
120 	return err;
121 
122 err_unmap:
123 	iounmap(mem);
124 	goto out;
125 }
126 
127 static void __exit mod_exit(void)
128 {
129 	void __iomem *mem = (void __iomem *)geode_rng.priv;
130 
131 	hwrng_unregister(&geode_rng);
132 	iounmap(mem);
133 }
134 
135 module_init(mod_init);
136 module_exit(mod_exit);
137 
138 MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
139 MODULE_LICENSE("GPL");
140