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
46static 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
61static 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
68static 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
80static 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
90static 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
98static 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	pr_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
126static 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
136static const struct of_device_id rng_match[] = {
137	{ .compatible      = "1682m-rng", },
138	{ .compatible      = "pasemi,pwrficient-rng", },
139	{ },
140};
141MODULE_DEVICE_TABLE(of, rng_match);
142
143static struct platform_driver rng_driver = {
144	.driver = {
145		.name = "pasemi-rng",
146		.of_match_table = rng_match,
147	},
148	.probe		= rng_probe,
149	.remove		= rng_remove,
150};
151
152module_platform_driver(rng_driver);
153
154MODULE_LICENSE("GPL");
155MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
156MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");
157