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9c3c133b AC |
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 | ||
08ced854 | 91 | static int __devinit timeriomem_rng_probe(struct platform_device *pdev) |
9c3c133b | 92 | { |
08ced854 | 93 | struct resource *res; |
9c3c133b AC |
94 | int ret; |
95 | ||
3341323b AC |
96 | res = platform_get_resource(pdev, IORESOURCE_MEM, 0); |
97 | ||
98 | if (!res) | |
99 | return -ENOENT; | |
100 | ||
9c3c133b AC |
101 | timeriomem_rng_data = pdev->dev.platform_data; |
102 | ||
3341323b AC |
103 | timeriomem_rng_data->address = ioremap(res->start, |
104 | res->end - res->start + 1); | |
08ced854 AC |
105 | if (!timeriomem_rng_data->address) |
106 | return -EIO; | |
3341323b | 107 | |
9c3c133b AC |
108 | if (timeriomem_rng_data->period != 0 |
109 | && usecs_to_jiffies(timeriomem_rng_data->period) > 0) { | |
110 | timeriomem_rng_timer.expires = jiffies; | |
111 | ||
112 | timeriomem_rng_ops.priv = usecs_to_jiffies( | |
113 | timeriomem_rng_data->period); | |
114 | } | |
115 | timeriomem_rng_data->present = 1; | |
116 | ||
117 | ret = hwrng_register(&timeriomem_rng_ops); | |
3341323b | 118 | if (ret) |
08ced854 | 119 | goto failed; |
9c3c133b AC |
120 | |
121 | dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n", | |
122 | timeriomem_rng_data->address, | |
123 | timeriomem_rng_data->period); | |
124 | ||
125 | return 0; | |
3341323b | 126 | |
08ced854 | 127 | failed: |
3341323b AC |
128 | dev_err(&pdev->dev, "problem registering\n"); |
129 | iounmap(timeriomem_rng_data->address); | |
3341323b AC |
130 | |
131 | return ret; | |
9c3c133b AC |
132 | } |
133 | ||
134 | static int __devexit timeriomem_rng_remove(struct platform_device *pdev) | |
135 | { | |
136 | del_timer_sync(&timeriomem_rng_timer); | |
137 | hwrng_unregister(&timeriomem_rng_ops); | |
138 | ||
3341323b | 139 | iounmap(timeriomem_rng_data->address); |
3341323b | 140 | |
9c3c133b AC |
141 | return 0; |
142 | } | |
143 | ||
144 | static struct platform_driver timeriomem_rng_driver = { | |
145 | .driver = { | |
146 | .name = "timeriomem_rng", | |
147 | .owner = THIS_MODULE, | |
148 | }, | |
149 | .probe = timeriomem_rng_probe, | |
150 | .remove = __devexit_p(timeriomem_rng_remove), | |
151 | }; | |
152 | ||
153 | static int __init timeriomem_rng_init(void) | |
154 | { | |
155 | return platform_driver_register(&timeriomem_rng_driver); | |
156 | } | |
157 | ||
158 | static void __exit timeriomem_rng_exit(void) | |
159 | { | |
160 | platform_driver_unregister(&timeriomem_rng_driver); | |
161 | } | |
162 | ||
163 | module_init(timeriomem_rng_init); | |
164 | module_exit(timeriomem_rng_exit); | |
165 | ||
166 | MODULE_LICENSE("GPL"); | |
167 | MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>"); | |
168 | MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver"); |