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