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/delay.h>
28 #include <linux/hw_random.h>
29 #include <linux/io.h>
30 #include <linux/kernel.h>
31 #include <linux/module.h>
32 #include <linux/pci.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 struct amd_geode_priv {
55 	struct pci_dev *pcidev;
56 	void __iomem *membase;
57 };
58 
59 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
60 {
61 	struct amd_geode_priv *priv = (struct amd_geode_priv *)rng->priv;
62 	void __iomem *mem = priv->membase;
63 
64 	*data = readl(mem + GEODE_RNG_DATA_REG);
65 
66 	return 4;
67 }
68 
69 static int geode_rng_data_present(struct hwrng *rng, int wait)
70 {
71 	struct amd_geode_priv *priv = (struct amd_geode_priv *)rng->priv;
72 	void __iomem *mem = priv->membase;
73 	int data, i;
74 
75 	for (i = 0; i < 20; i++) {
76 		data = !!(readl(mem + GEODE_RNG_STATUS_REG));
77 		if (data || !wait)
78 			break;
79 		udelay(10);
80 	}
81 	return data;
82 }
83 
84 
85 static struct hwrng geode_rng = {
86 	.name		= "geode",
87 	.data_present	= geode_rng_data_present,
88 	.data_read	= geode_rng_data_read,
89 };
90 
91 
92 static int __init geode_rng_init(void)
93 {
94 	int err = -ENODEV;
95 	struct pci_dev *pdev = NULL;
96 	const struct pci_device_id *ent;
97 	void __iomem *mem;
98 	unsigned long rng_base;
99 	struct amd_geode_priv *priv;
100 
101 	for_each_pci_dev(pdev) {
102 		ent = pci_match_id(pci_tbl, pdev);
103 		if (ent)
104 			goto found;
105 	}
106 	/* Device not found. */
107 	return err;
108 
109 found:
110 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
111 	if (!priv) {
112 		err = -ENOMEM;
113 		goto put_dev;
114 	}
115 
116 	rng_base = pci_resource_start(pdev, 0);
117 	if (rng_base == 0)
118 		goto free_priv;
119 	err = -ENOMEM;
120 	mem = ioremap(rng_base, 0x58);
121 	if (!mem)
122 		goto free_priv;
123 
124 	geode_rng.priv = (unsigned long)priv;
125 	priv->membase = mem;
126 	priv->pcidev = pdev;
127 
128 	pr_info("AMD Geode RNG detected\n");
129 	err = hwrng_register(&geode_rng);
130 	if (err) {
131 		pr_err(PFX "RNG registering failed (%d)\n",
132 		       err);
133 		goto err_unmap;
134 	}
135 	return err;
136 
137 err_unmap:
138 	iounmap(mem);
139 free_priv:
140 	kfree(priv);
141 put_dev:
142 	pci_dev_put(pdev);
143 	return err;
144 }
145 
146 static void __exit geode_rng_exit(void)
147 {
148 	struct amd_geode_priv *priv;
149 
150 	priv = (struct amd_geode_priv *)geode_rng.priv;
151 	hwrng_unregister(&geode_rng);
152 	iounmap(priv->membase);
153 	pci_dev_put(priv->pcidev);
154 	kfree(priv);
155 }
156 
157 module_init(geode_rng_init);
158 module_exit(geode_rng_exit);
159 
160 MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
161 MODULE_LICENSE("GPL");
162