summaryrefslogtreecommitdiff
path: root/drivers/char/hw_random/atmel-rng.c
blob: 433426242b875c7297573e7985afabcdb569d25c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
/*
 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/hw_random.h>
#include <linux/platform_device.h>

#define TRNG_CR		0x00
#define TRNG_ISR	0x1c
#define TRNG_ODATA	0x50

#define TRNG_KEY	0x524e4700 /* RNG */

struct atmel_trng {
	struct clk *clk;
	void __iomem *base;
	struct hwrng rng;
};

static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
			   bool wait)
{
	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
	u32 *data = buf;

	/* data ready? */
	if (readl(trng->base + TRNG_ISR) & 1) {
		*data = readl(trng->base + TRNG_ODATA);
		/*
		  ensure data ready is only set again AFTER the next data
		  word is ready in case it got set between checking ISR
		  and reading ODATA, so we don't risk re-reading the
		  same word
		*/
		readl(trng->base + TRNG_ISR);
		return 4;
	} else
		return 0;
}

static void atmel_trng_enable(struct atmel_trng *trng)
{
	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
}

static void atmel_trng_disable(struct atmel_trng *trng)
{
	writel(TRNG_KEY, trng->base + TRNG_CR);
}

static int atmel_trng_probe(struct platform_device *pdev)
{
	struct atmel_trng *trng;
	struct resource *res;
	int ret;

	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
	if (!trng)
		return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	trng->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(trng->base))
		return PTR_ERR(trng->base);

	trng->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(trng->clk))
		return PTR_ERR(trng->clk);

	ret = clk_prepare_enable(trng->clk);
	if (ret)
		return ret;

	atmel_trng_enable(trng);
	trng->rng.name = pdev->name;
	trng->rng.read = atmel_trng_read;

	ret = hwrng_register(&trng->rng);
	if (ret)
		goto err_register;

	platform_set_drvdata(pdev, trng);

	return 0;

err_register:
	clk_disable_unprepare(trng->clk);
	return ret;
}

static int atmel_trng_remove(struct platform_device *pdev)
{
	struct atmel_trng *trng = platform_get_drvdata(pdev);

	hwrng_unregister(&trng->rng);

	atmel_trng_disable(trng);
	clk_disable_unprepare(trng->clk);

	return 0;
}

#ifdef CONFIG_PM
static int atmel_trng_suspend(struct device *dev)
{
	struct atmel_trng *trng = dev_get_drvdata(dev);

	atmel_trng_disable(trng);
	clk_disable_unprepare(trng->clk);

	return 0;
}

static int atmel_trng_resume(struct device *dev)
{
	struct atmel_trng *trng = dev_get_drvdata(dev);
	int ret;

	ret = clk_prepare_enable(trng->clk);
	if (ret)
		return ret;

	atmel_trng_enable(trng);

	return 0;
}

static const struct dev_pm_ops atmel_trng_pm_ops = {
	.suspend	= atmel_trng_suspend,
	.resume		= atmel_trng_resume,
};
#endif /* CONFIG_PM */

static const struct of_device_id atmel_trng_dt_ids[] = {
	{ .compatible = "atmel,at91sam9g45-trng" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);

static struct platform_driver atmel_trng_driver = {
	.probe		= atmel_trng_probe,
	.remove		= atmel_trng_remove,
	.driver		= {
		.name	= "atmel-trng",
#ifdef CONFIG_PM
		.pm	= &atmel_trng_pm_ops,
#endif /* CONFIG_PM */
		.of_match_table = atmel_trng_dt_ids,
	},
};

module_platform_driver(atmel_trng_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
MODULE_DESCRIPTION("Atmel true random number generator driver");