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 <linux/of_address.h>
28 #include <linux/of_platform.h>
29 #include <asm/io.h>
30 
31 #define SDCRNG_CTL_REG			0x00
32 #define   SDCRNG_CTL_FVLD_M		0x0000f000
33 #define   SDCRNG_CTL_FVLD_S		12
34 #define   SDCRNG_CTL_KSZ		0x00000800
35 #define   SDCRNG_CTL_RSRC_CRG		0x00000010
36 #define   SDCRNG_CTL_RSRC_RRG		0x00000000
37 #define   SDCRNG_CTL_CE			0x00000004
38 #define   SDCRNG_CTL_RE			0x00000002
39 #define   SDCRNG_CTL_DR			0x00000001
40 #define   SDCRNG_CTL_SELECT_RRG_RNG	(SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
41 #define   SDCRNG_CTL_SELECT_CRG_RNG	(SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
42 #define SDCRNG_VAL_REG			0x20
43 
44 #define MODULE_NAME "pasemi_rng"
45 
46 static int pasemi_rng_data_present(struct hwrng *rng, int wait)
47 {
48 	void __iomem *rng_regs = (void __iomem *)rng->priv;
49 	int data, i;
50 
51 	for (i = 0; i < 20; i++) {
52 		data = (in_le32(rng_regs + SDCRNG_CTL_REG)
53 			& SDCRNG_CTL_FVLD_M) ? 1 : 0;
54 		if (data || !wait)
55 			break;
56 		udelay(10);
57 	}
58 	return data;
59 }
60 
61 static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
62 {
63 	void __iomem *rng_regs = (void __iomem *)rng->priv;
64 	*data = in_le32(rng_regs + SDCRNG_VAL_REG);
65 	return 4;
66 }
67 
68 static int pasemi_rng_init(struct hwrng *rng)
69 {
70 	void __iomem *rng_regs = (void __iomem *)rng->priv;
71 	u32 ctl;
72 
73 	ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
74 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
75 	out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);
76 
77 	return 0;
78 }
79 
80 static void pasemi_rng_cleanup(struct hwrng *rng)
81 {
82 	void __iomem *rng_regs = (void __iomem *)rng->priv;
83 	u32 ctl;
84 
85 	ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
86 	out_le32(rng_regs + SDCRNG_CTL_REG,
87 		 in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
88 }
89 
90 static struct hwrng pasemi_rng = {
91 	.name		= MODULE_NAME,
92 	.init		= pasemi_rng_init,
93 	.cleanup	= pasemi_rng_cleanup,
94 	.data_present	= pasemi_rng_data_present,
95 	.data_read	= pasemi_rng_data_read,
96 };
97 
98 static int rng_probe(struct platform_device *ofdev)
99 {
100 	void __iomem *rng_regs;
101 	struct device_node *rng_np = ofdev->dev.of_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 rng_remove(struct platform_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 platform_driver rng_driver = {
143 	.driver = {
144 		.name = "pasemi-rng",
145 		.owner = THIS_MODULE,
146 		.of_match_table = rng_match,
147 	},
148 	.probe		= rng_probe,
149 	.remove		= rng_remove,
150 };
151 
152 module_platform_driver(rng_driver);
153 
154 MODULE_LICENSE("GPL");
155 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
156 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");
157