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_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 rng_probe(struct platform_device *ofdev)
98 {
99 	void __iomem *rng_regs;
100 	struct device_node *rng_np = ofdev->dev.of_node;
101 	struct resource res;
102 	int err = 0;
103 
104 	err = of_address_to_resource(rng_np, 0, &res);
105 	if (err)
106 		return -ENODEV;
107 
108 	rng_regs = ioremap(res.start, 0x100);
109 
110 	if (!rng_regs)
111 		return -ENOMEM;
112 
113 	pasemi_rng.priv = (unsigned long)rng_regs;
114 
115 	printk(KERN_INFO "Registering PA Semi RNG\n");
116 
117 	err = hwrng_register(&pasemi_rng);
118 
119 	if (err)
120 		iounmap(rng_regs);
121 
122 	return err;
123 }
124 
125 static int rng_remove(struct platform_device *dev)
126 {
127 	void __iomem *rng_regs = (void __iomem *)pasemi_rng.priv;
128 
129 	hwrng_unregister(&pasemi_rng);
130 	iounmap(rng_regs);
131 
132 	return 0;
133 }
134 
135 static struct of_device_id rng_match[] = {
136 	{ .compatible      = "1682m-rng", },
137 	{ .compatible      = "pasemi,pwrficient-rng", },
138 	{ },
139 };
140 
141 static struct platform_driver rng_driver = {
142 	.driver = {
143 		.name = "pasemi-rng",
144 		.owner = THIS_MODULE,
145 		.of_match_table = rng_match,
146 	},
147 	.probe		= rng_probe,
148 	.remove		= rng_remove,
149 };
150 
151 module_platform_driver(rng_driver);
152 
153 MODULE_LICENSE("GPL");
154 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
155 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");
156