tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/of.h>
27#include <linux/hw_random.h>
28#include <linux/io.h>
29#include <linux/slab.h>
30#include <linux/timeriomem-rng.h>
31#include <linux/jiffies.h>
32#include <linux/sched.h>
33#include <linux/timer.h>
34#include <linux/completion.h>
35
36struct timeriomem_rng_private_data {
37 void __iomem *io_base;
38 unsigned int expires;
39 unsigned int period;
40 unsigned int present:1;
41
42 struct timer_list timer;
43 struct completion completion;
44
45 struct hwrng timeriomem_rng_ops;
46};
47
48#define to_rng_priv(rng) \
49 ((struct timeriomem_rng_private_data *)rng->priv)
50
51/*
52 * have data return 1, however return 0 if we have nothing
53 */
54static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
55{
56 struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
57
58 if (!wait || priv->present)
59 return priv->present;
60
61 wait_for_completion(&priv->completion);
62
63 return 1;
64}
65
66static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
67{
68 struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
69 unsigned long cur;
70 s32 delay;
71
72 *data = readl(priv->io_base);
73
74 cur = jiffies;
75
76 delay = cur - priv->expires;
77 delay = priv->period - (delay % priv->period);
78
79 priv->expires = cur + delay;
80 priv->present = 0;
81
82 reinit_completion(&priv->completion);
83 mod_timer(&priv->timer, priv->expires);
84
85 return 4;
86}
87
88static void timeriomem_rng_trigger(unsigned long data)
89{
90 struct timeriomem_rng_private_data *priv
91 = (struct timeriomem_rng_private_data *)data;
92
93 priv->present = 1;
94 complete(&priv->completion);
95}
96
97static int timeriomem_rng_probe(struct platform_device *pdev)
98{
99 struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
100 struct timeriomem_rng_private_data *priv;
101 struct resource *res;
102 int err = 0;
103 int period;
104
105 if (!pdev->dev.of_node && !pdata) {
106 dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
107 return -EINVAL;
108 }
109
110 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
111 if (!res)
112 return -ENXIO;
113
114 if (res->start % 4 != 0 || resource_size(res) != 4) {
115 dev_err(&pdev->dev,
116 "address must be four bytes wide and aligned\n");
117 return -EINVAL;
118 }
119
120 /* Allocate memory for the device structure (and zero it) */
121 priv = devm_kzalloc(&pdev->dev,
122 sizeof(struct timeriomem_rng_private_data), GFP_KERNEL);
123 if (!priv) {
124 dev_err(&pdev->dev, "failed to allocate device structure.\n");
125 return -ENOMEM;
126 }
127
128 platform_set_drvdata(pdev, priv);
129
130 if (pdev->dev.of_node) {
131 int i;
132
133 if (!of_property_read_u32(pdev->dev.of_node,
134 "period", &i))
135 period = i;
136 else {
137 dev_err(&pdev->dev, "missing period\n");
138 return -EINVAL;
139 }
140 } else {
141 period = pdata->period;
142 }
143
144 priv->period = usecs_to_jiffies(period);
145 if (priv->period < 1) {
146 dev_err(&pdev->dev, "period is less than one jiffy\n");
147 return -EINVAL;
148 }
149
150 priv->expires = jiffies;
151 priv->present = 1;
152
153 init_completion(&priv->completion);
154 complete(&priv->completion);
155
156 setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
157
158 priv->timeriomem_rng_ops.name = dev_name(&pdev->dev);
159 priv->timeriomem_rng_ops.data_present = timeriomem_rng_data_present;
160 priv->timeriomem_rng_ops.data_read = timeriomem_rng_data_read;
161 priv->timeriomem_rng_ops.priv = (unsigned long)priv;
162
163 priv->io_base = devm_ioremap_resource(&pdev->dev, res);
164 if (IS_ERR(priv->io_base)) {
165 err = PTR_ERR(priv->io_base);
166 goto out_timer;
167 }
168
169 err = hwrng_register(&priv->timeriomem_rng_ops);
170 if (err) {
171 dev_err(&pdev->dev, "problem registering\n");
172 goto out_timer;
173 }
174
175 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
176 priv->io_base, period);
177
178 return 0;
179
180out_timer:
181 del_timer_sync(&priv->timer);
182 return err;
183}
184
185static int timeriomem_rng_remove(struct platform_device *pdev)
186{
187 struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
188
189 hwrng_unregister(&priv->timeriomem_rng_ops);
190
191 del_timer_sync(&priv->timer);
192
193 return 0;
194}
195
196static const struct of_device_id timeriomem_rng_match[] = {
197 { .compatible = "timeriomem_rng" },
198 {},
199};
200MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
201
202static struct platform_driver timeriomem_rng_driver = {
203 .driver = {
204 .name = "timeriomem_rng",
205 .owner = THIS_MODULE,
206 .of_match_table = timeriomem_rng_match,
207 },
208 .probe = timeriomem_rng_probe,
209 .remove = timeriomem_rng_remove,
210};
211
212module_platform_driver(timeriomem_rng_driver);
213
214MODULE_LICENSE("GPL");
215MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
216MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");