media: tegra: enable a clock for VIP in APB MISC register
[linux-2.6.git] / 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
34 static struct timeriomem_rng_data *timeriomem_rng_data;
35
36 static void timeriomem_rng_trigger(unsigned long);
37 static 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  */
42 static 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
55 static 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
78 static void timeriomem_rng_trigger(unsigned long dummy)
79 {
80         timeriomem_rng_data->present = 1;
81         complete(&timeriomem_rng_data->completion);
82 }
83
84 static 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
91 static int __devinit 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
126 failed:
127         dev_err(&pdev->dev, "problem registering\n");
128         iounmap(timeriomem_rng_data->address);
129
130         return ret;
131 }
132
133 static int __devexit 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
143 static struct platform_driver timeriomem_rng_driver = {
144         .driver = {
145                 .name           = "timeriomem_rng",
146                 .owner          = THIS_MODULE,
147         },
148         .probe          = timeriomem_rng_probe,
149         .remove         = __devexit_p(timeriomem_rng_remove),
150 };
151
152 static int __init timeriomem_rng_init(void)
153 {
154         return platform_driver_register(&timeriomem_rng_driver);
155 }
156
157 static void __exit timeriomem_rng_exit(void)
158 {
159         platform_driver_unregister(&timeriomem_rng_driver);
160 }
161
162 module_init(timeriomem_rng_init);
163 module_exit(timeriomem_rng_exit);
164
165 MODULE_LICENSE("GPL");
166 MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
167 MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");