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

1/*
2 * drivers/char/hw_random/timeriomem-rng.c
3 *
4 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
5 *
6 * Derived from drivers/char/hw_random/omap-rng.c
7 * Copyright 2005 (c) MontaVista Software, Inc.
8 * Author: Deepak Saxena <dsaxena@plexity.net>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 * Overview:
15 * This driver is useful for platforms that have an IO range that provides
16 * periodic random data from a single IO memory address. All the platform
17 * has to do is provide the address and 'wait time' that new data becomes
18 * available.
19 *
20 * TODO: add support for reading sizes other than 32bits and masking
21 */
22
23#include <linux/module.h>
24#include <linux/kernel.h>
25#include <linux/platform_device.h>
26#include <linux/hw_random.h>
27#include <linux/io.h>
28#include <linux/timeriomem-rng.h>
29#include <linux/jiffies.h>
30#include <linux/sched.h>
31#include <linux/timer.h>
32#include <linux/completion.h>
33
34static struct timeriomem_rng_data *timeriomem_rng_data;
35
36static void timeriomem_rng_trigger(unsigned long);
37static DEFINE_TIMER(timeriomem_rng_timer, timeriomem_rng_trigger, 0, 0);
38
39/*
40 * have data return 1, however return 0 if we have nothing
41 */
42static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
43{
44    if (rng->priv == 0)
45        return 1;
46
47    if (!wait || timeriomem_rng_data->present)
48        return timeriomem_rng_data->present;
49
50    wait_for_completion(&timeriomem_rng_data->completion);
51
52    return 1;
53}
54
55static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
56{
57    unsigned long cur;
58    s32 delay;
59
60    *data = readl(timeriomem_rng_data->address);
61
62    if (rng->priv != 0) {
63        cur = jiffies;
64
65        delay = cur - timeriomem_rng_timer.expires;
66        delay = rng->priv - (delay % rng->priv);
67
68        timeriomem_rng_timer.expires = cur + delay;
69        timeriomem_rng_data->present = 0;
70
71        init_completion(&timeriomem_rng_data->completion);
72        add_timer(&timeriomem_rng_timer);
73    }
74
75    return 4;
76}
77
78static void timeriomem_rng_trigger(unsigned long dummy)
79{
80    timeriomem_rng_data->present = 1;
81    complete(&timeriomem_rng_data->completion);
82}
83
84static struct hwrng timeriomem_rng_ops = {
85    .name = "timeriomem",
86    .data_present = timeriomem_rng_data_present,
87    .data_read = timeriomem_rng_data_read,
88    .priv = 0,
89};
90
91static int timeriomem_rng_probe(struct platform_device *pdev)
92{
93    struct resource *res;
94    int ret;
95
96    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
97
98    if (!res)
99        return -ENOENT;
100
101    timeriomem_rng_data = pdev->dev.platform_data;
102
103    timeriomem_rng_data->address = ioremap(res->start, resource_size(res));
104    if (!timeriomem_rng_data->address)
105        return -EIO;
106
107    if (timeriomem_rng_data->period != 0
108        && usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
109        timeriomem_rng_timer.expires = jiffies;
110
111        timeriomem_rng_ops.priv = usecs_to_jiffies(
112                        timeriomem_rng_data->period);
113    }
114    timeriomem_rng_data->present = 1;
115
116    ret = hwrng_register(&timeriomem_rng_ops);
117    if (ret)
118        goto failed;
119
120    dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
121            timeriomem_rng_data->address,
122            timeriomem_rng_data->period);
123
124    return 0;
125
126failed:
127    dev_err(&pdev->dev, "problem registering\n");
128    iounmap(timeriomem_rng_data->address);
129
130    return ret;
131}
132
133static int timeriomem_rng_remove(struct platform_device *pdev)
134{
135    del_timer_sync(&timeriomem_rng_timer);
136    hwrng_unregister(&timeriomem_rng_ops);
137
138    iounmap(timeriomem_rng_data->address);
139
140    return 0;
141}
142
143static struct platform_driver timeriomem_rng_driver = {
144    .driver = {
145        .name = "timeriomem_rng",
146        .owner = THIS_MODULE,
147    },
148    .probe = timeriomem_rng_probe,
149    .remove = timeriomem_rng_remove,
150};
151
152module_platform_driver(timeriomem_rng_driver);
153
154MODULE_LICENSE("GPL");
155MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
156MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
157

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