1 /*
2  * Copyright (C) 2006-2007 PA Semi, Inc
3  *
4  * Maintained by: Olof Johansson <olof@lixom.net>
5  *
6  * Driver for the PWRficient onchip rng
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, write to the Free Software
19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
20  */
21 
22 #include <linux/module.h>
23 #include <linux/kernel.h>
24 #include <linux/platform_device.h>
25 #include <linux/hw_random.h>
26 #include <linux/delay.h>
27 #include <asm/of_platform.h>
28 #include <asm/io.h>
29 
30 #define SDCRNG_CTL_REG			0x00
31 #define   SDCRNG_CTL_FVLD_M		0x0000f000
32 #define   SDCRNG_CTL_FVLD_S		12
33 #define   SDCRNG_CTL_KSZ		0x00000800
34 #define   SDCRNG_CTL_RSRC_CRG		0x00000010
35 #define   SDCRNG_CTL_RSRC_RRG		0x00000000
36 #define   SDCRNG_CTL_CE			0x00000004
37 #define   SDCRNG_CTL_RE			0x00000002
38 #define   SDCRNG_CTL_DR			0x00000001
39 #define   SDCRNG_CTL_SELECT_RRG_RNG	(SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
40 #define   SDCRNG_CTL_SELECT_CRG_RNG	(SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
41 #define SDCRNG_VAL_REG			0x20
42 
43 #define MODULE_NAME "pasemi_rng"
44 
45 static int pasemi_rng_data_present(struct hwrng *rng, int wait)
46 {
47 	void __iomem *rng_regs = (void __iomem *)rng->priv;
48 	int data, i;
49 
50 	for (i = 0; i < 20; i++) {
51 		data = (in_le32(rng_regs + SDCRNG_CTL_REG)
52 			& SDCRNG_CTL_FVLD_M) ? 1 : 0;
53 		if (data || !wait)
54 			break;
55 		udelay(10);
56 	}
57 	return data;
58 }
59 
60 static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
61 {
62 	void __iomem *rng_regs = (void __iomem *)rng->priv;
63 	*data = in_le32(rng_regs + SDCRNG_VAL_REG);
64 	return 4;
65 }
66 
67 static int pasemi_rng_init(struct hwrng *rng)
68 {
69 	void __iomem *rng_regs = (void __iomem *)rng->priv;
70 	u32 ctl;
71 
72 	ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
73 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
74 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);
75 
76 	return 0;
77 }
78 
79 static void pasemi_rng_cleanup(struct hwrng *rng)
80 {
81 	void __iomem *rng_regs = (void __iomem *)rng->priv;
82 	u32 ctl;
83 
84 	ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
85 	out_le32(rng_regs + SDCRNG_CTL_REG,
86 		 in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
87 }
88 
89 static struct hwrng pasemi_rng = {
90 	.name		= MODULE_NAME,
91 	.init		= pasemi_rng_init,
92 	.cleanup	= pasemi_rng_cleanup,
93 	.data_present	= pasemi_rng_data_present,
94 	.data_read	= pasemi_rng_data_read,
95 };
96 
97 static int __devinit rng_probe(struct of_device *ofdev,
98 			       const struct of_device_id *match)
99 {
100 	void __iomem *rng_regs;
101 	struct device_node *rng_np = ofdev->node;
102 	struct resource res;
103 	int err = 0;
104 
105 	err = of_address_to_resource(rng_np, 0, &res);
106 	if (err)
107 		return -ENODEV;
108 
109 	rng_regs = ioremap(res.start, 0x100);
110 
111 	if (!rng_regs)
112 		return -ENOMEM;
113 
114 	pasemi_rng.priv = (unsigned long)rng_regs;
115 
116 	printk(KERN_INFO "Registering PA Semi RNG\n");
117 
118 	err = hwrng_register(&pasemi_rng);
119 
120 	if (err)
121 		iounmap(rng_regs);
122 
123 	return err;
124 }
125 
126 static int __devexit rng_remove(struct of_device *dev)
127 {
128 	void __iomem *rng_regs = (void __iomem *)pasemi_rng.priv;
129 
130 	hwrng_unregister(&pasemi_rng);
131 	iounmap(rng_regs);
132 
133 	return 0;
134 }
135 
136 static struct of_device_id rng_match[] = {
137 	{ .compatible      = "1682m-rng", },
138 	{ .compatible      = "pasemi,pwrficient-rng", },
139 	{ },
140 };
141 
142 static struct of_platform_driver rng_driver = {
143 	.name		= "pasemi-rng",
144 	.match_table	= rng_match,
145 	.probe		= rng_probe,
146 	.remove		= rng_remove,
147 };
148 
149 static int __init rng_init(void)
150 {
151 	return of_register_platform_driver(&rng_driver);
152 }
153 module_init(rng_init);
154 
155 static void __exit rng_exit(void)
156 {
157 	of_unregister_platform_driver(&rng_driver);
158 }
159 module_exit(rng_exit);
160 
161 MODULE_LICENSE("GPL");
162 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
163 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");
164