summaryrefslogtreecommitdiffstats
path: root/drivers/char/hw_random/timeriomem-rng.c
blob: d2120ba8f3f962444dee50ba69fbd57ec16a716a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
/*
 * drivers/char/hw_random/timeriomem-rng.c
 *
 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
 *
 * Derived from drivers/char/hw_random/omap-rng.c
 *   Copyright 2005 (c) MontaVista Software, Inc.
 *   Author: Deepak Saxena <dsaxena@plexity.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Overview:
 *   This driver is useful for platforms that have an IO range that provides
 *   periodic random data from a single IO memory address.  All the platform
 *   has to do is provide the address and 'wait time' that new data becomes
 *   available.
 *
 * TODO: add support for reading sizes other than 32bits and masking
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/timeriomem-rng.h>
#include <linux/jiffies.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/completion.h>

struct timeriomem_rng_private_data {
	void __iomem		*io_base;
	unsigned int		expires;
	unsigned int		period;
	unsigned int		present:1;

	struct timer_list	timer;
	struct completion	completion;

	struct hwrng		timeriomem_rng_ops;
};

#define to_rng_priv(rng) \
		((struct timeriomem_rng_private_data *)rng->priv)

/*
 * have data return 1, however return 0 if we have nothing
 */
static int timeriomem_rng_data_present(struct hwrng *rng, int wait)
{
	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);

	if (!wait || priv->present)
		return priv->present;

	wait_for_completion(&priv->completion);

	return 1;
}

static int timeriomem_rng_data_read(struct hwrng *rng, u32 *data)
{
	struct timeriomem_rng_private_data *priv = to_rng_priv(rng);
	unsigned long cur;
	s32 delay;

	*data = readl(priv->io_base);

	cur = jiffies;

	delay = cur - priv->expires;
	delay = priv->period - (delay % priv->period);

	priv->expires = cur + delay;
	priv->present = 0;

	INIT_COMPLETION(priv->completion);
	mod_timer(&priv->timer, priv->expires);

	return 4;
}

static void timeriomem_rng_trigger(unsigned long data)
{
	struct timeriomem_rng_private_data *priv
			= (struct timeriomem_rng_private_data *)data;

	priv->present = 1;
	complete(&priv->completion);
}

static int timeriomem_rng_probe(struct platform_device *pdev)
{
	struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
	struct timeriomem_rng_private_data *priv;
	struct resource *res;
	int err = 0;
	int period;

	if (!pdev->dev.of_node && !pdata) {
		dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
		return -EINVAL;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENXIO;

	if (res->start % 4 != 0 || resource_size(res) != 4) {
		dev_err(&pdev->dev,
			"address must be four bytes wide and aligned\n");
		return -EINVAL;
	}

	/* Allocate memory for the device structure (and zero it) */
	priv = kzalloc(sizeof(struct timeriomem_rng_private_data), GFP_KERNEL);
	if (!priv) {
		dev_err(&pdev->dev, "failed to allocate device structure.\n");
		return -ENOMEM;
	}

	platform_set_drvdata(pdev, priv);

	if (pdev->dev.of_node) {
		int i;

		if (!of_property_read_u32(pdev->dev.of_node,
						"period", &i))
			period = i;
		else {
			dev_err(&pdev->dev, "missing period\n");
			err = -EINVAL;
			goto out_free;
		}
	} else
		period = pdata->period;

	priv->period = usecs_to_jiffies(period);
	if (priv->period < 1) {
		dev_err(&pdev->dev, "period is less than one jiffy\n");
		err = -EINVAL;
		goto out_free;
	}

	priv->expires	= jiffies;
	priv->present	= 1;

	init_completion(&priv->completion);
	complete(&priv->completion);

	setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);

	priv->timeriomem_rng_ops.name		= dev_name(&pdev->dev);
	priv->timeriomem_rng_ops.data_present	= timeriomem_rng_data_present;
	priv->timeriomem_rng_ops.data_read	= timeriomem_rng_data_read;
	priv->timeriomem_rng_ops.priv		= (unsigned long)priv;

	if (!request_mem_region(res->start, resource_size(res),
				dev_name(&pdev->dev))) {
		dev_err(&pdev->dev, "request_mem_region failed\n");
		err = -EBUSY;
		goto out_timer;
	}

	priv->io_base = ioremap(res->start, resource_size(res));
	if (priv->io_base == NULL) {
		dev_err(&pdev->dev, "ioremap failed\n");
		err = -EIO;
		goto out_release_io;
	}

	err = hwrng_register(&priv->timeriomem_rng_ops);
	if (err) {
		dev_err(&pdev->dev, "problem registering\n");
		goto out;
	}

	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
			priv->io_base, period);

	return 0;

out:
	iounmap(priv->io_base);
out_release_io:
	release_mem_region(res->start, resource_size(res));
out_timer:
	del_timer_sync(&priv->timer);
out_free:
	kfree(priv);
	return err;
}

static int timeriomem_rng_remove(struct platform_device *pdev)
{
	struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
	struct resource *res;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	hwrng_unregister(&priv->timeriomem_rng_ops);

	del_timer_sync(&priv->timer);
	iounmap(priv->io_base);
	release_mem_region(res->start, resource_size(res));
	kfree(priv);

	return 0;
}

static const struct of_device_id timeriomem_rng_match[] = {
	{ .compatible = "timeriomem_rng" },
	{},
};
MODULE_DEVICE_TABLE(of, timeriomem_rng_match);

static struct platform_driver timeriomem_rng_driver = {
	.driver = {
		.name		= "timeriomem_rng",
		.owner		= THIS_MODULE,
		.of_match_table	= timeriomem_rng_match,
	},
	.probe		= timeriomem_rng_probe,
	.remove		= timeriomem_rng_remove,
};

module_platform_driver(timeriomem_rng_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");