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 */
timeriomem_rng_data_present(struct hwrng * rng,int wait)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
timeriomem_rng_data_read(struct hwrng * rng,u32 * data)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
timeriomem_rng_trigger(unsigned long dummy)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
timeriomem_rng_probe(struct platform_device * pdev)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,
104 res->end - res->start + 1);
105 if (!timeriomem_rng_data->address)
106 return -EIO;
107
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);
118 if (ret)
119 goto failed;
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;
126
127 failed:
128 dev_err(&pdev->dev, "problem registering\n");
129 iounmap(timeriomem_rng_data->address);
130
131 return ret;
132 }
133
timeriomem_rng_remove(struct platform_device * pdev)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
139 iounmap(timeriomem_rng_data->address);
140
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
timeriomem_rng_init(void)153 static int __init timeriomem_rng_init(void)
154 {
155 return platform_driver_register(&timeriomem_rng_driver);
156 }
157
timeriomem_rng_exit(void)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");
169