Root/drivers/char/hw_random/atmel-rng.c

1/*
2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
3 *
4 * This file is licensed under the terms of the GNU General Public
5 * License version 2. This program is licensed "as is" without any
6 * warranty of any kind, whether express or implied.
7 */
8
9#include <linux/kernel.h>
10#include <linux/module.h>
11#include <linux/slab.h>
12#include <linux/err.h>
13#include <linux/clk.h>
14#include <linux/io.h>
15#include <linux/hw_random.h>
16#include <linux/platform_device.h>
17
18#define TRNG_CR 0x00
19#define TRNG_ISR 0x1c
20#define TRNG_ODATA 0x50
21
22#define TRNG_KEY 0x524e4700 /* RNG */
23
24struct atmel_trng {
25    struct clk *clk;
26    void __iomem *base;
27    struct hwrng rng;
28};
29
30static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
31               bool wait)
32{
33    struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
34    u32 *data = buf;
35
36    /* data ready? */
37    if (readl(trng->base + TRNG_ISR) & 1) {
38        *data = readl(trng->base + TRNG_ODATA);
39        /*
40          ensure data ready is only set again AFTER the next data
41          word is ready in case it got set between checking ISR
42          and reading ODATA, so we don't risk re-reading the
43          same word
44        */
45        readl(trng->base + TRNG_ISR);
46        return 4;
47    } else
48        return 0;
49}
50
51static int atmel_trng_probe(struct platform_device *pdev)
52{
53    struct atmel_trng *trng;
54    struct resource *res;
55    int ret;
56
57    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
58    if (!res)
59        return -EINVAL;
60
61    trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
62    if (!trng)
63        return -ENOMEM;
64
65    if (!devm_request_mem_region(&pdev->dev, res->start,
66                     resource_size(res), pdev->name))
67        return -EBUSY;
68
69    trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
70    if (!trng->base)
71        return -EBUSY;
72
73    trng->clk = clk_get(&pdev->dev, NULL);
74    if (IS_ERR(trng->clk))
75        return PTR_ERR(trng->clk);
76
77    ret = clk_enable(trng->clk);
78    if (ret)
79        goto err_enable;
80
81    writel(TRNG_KEY | 1, trng->base + TRNG_CR);
82    trng->rng.name = pdev->name;
83    trng->rng.read = atmel_trng_read;
84
85    ret = hwrng_register(&trng->rng);
86    if (ret)
87        goto err_register;
88
89    platform_set_drvdata(pdev, trng);
90
91    return 0;
92
93err_register:
94    clk_disable(trng->clk);
95err_enable:
96    clk_put(trng->clk);
97
98    return ret;
99}
100
101static int atmel_trng_remove(struct platform_device *pdev)
102{
103    struct atmel_trng *trng = platform_get_drvdata(pdev);
104
105    hwrng_unregister(&trng->rng);
106
107    writel(TRNG_KEY, trng->base + TRNG_CR);
108    clk_disable(trng->clk);
109    clk_put(trng->clk);
110
111    platform_set_drvdata(pdev, NULL);
112
113    return 0;
114}
115
116#ifdef CONFIG_PM
117static int atmel_trng_suspend(struct device *dev)
118{
119    struct atmel_trng *trng = dev_get_drvdata(dev);
120
121    clk_disable(trng->clk);
122
123    return 0;
124}
125
126static int atmel_trng_resume(struct device *dev)
127{
128    struct atmel_trng *trng = dev_get_drvdata(dev);
129
130    return clk_enable(trng->clk);
131}
132
133static const struct dev_pm_ops atmel_trng_pm_ops = {
134    .suspend = atmel_trng_suspend,
135    .resume = atmel_trng_resume,
136};
137#endif /* CONFIG_PM */
138
139static struct platform_driver atmel_trng_driver = {
140    .probe = atmel_trng_probe,
141    .remove = atmel_trng_remove,
142    .driver = {
143        .name = "atmel-trng",
144        .owner = THIS_MODULE,
145#ifdef CONFIG_PM
146        .pm = &atmel_trng_pm_ops,
147#endif /* CONFIG_PM */
148    },
149};
150
151module_platform_driver(atmel_trng_driver);
152
153MODULE_LICENSE("GPL");
154MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
155MODULE_DESCRIPTION("Atmel true random number generator driver");
156

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