[go: nahoru, domu]
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		return -ENOMEM;
125
126	platform_set_drvdata(pdev, priv);
127
128	if (pdev->dev.of_node) {
129		int i;
130
131		if (!of_property_read_u32(pdev->dev.of_node,
132						"period", &i))
133			period = i;
134		else {
135			dev_err(&pdev->dev, "missing period\n");
136			return -EINVAL;
137		}
138	} else {
139		period = pdata->period;
140	}
141
142	priv->period = usecs_to_jiffies(period);
143	if (priv->period < 1) {
144		dev_err(&pdev->dev, "period is less than one jiffy\n");
145		return -EINVAL;
146	}
147
148	priv->expires	= jiffies;
149	priv->present	= 1;
150
151	init_completion(&priv->completion);
152	complete(&priv->completion);
153
154	setup_timer(&priv->timer, timeriomem_rng_trigger, (unsigned long)priv);
155
156	priv->timeriomem_rng_ops.name		= dev_name(&pdev->dev);
157	priv->timeriomem_rng_ops.data_present	= timeriomem_rng_data_present;
158	priv->timeriomem_rng_ops.data_read	= timeriomem_rng_data_read;
159	priv->timeriomem_rng_ops.priv		= (unsigned long)priv;
160
161	priv->io_base = devm_ioremap_resource(&pdev->dev, res);
162	if (IS_ERR(priv->io_base)) {
163		err = PTR_ERR(priv->io_base);
164		goto out_timer;
165	}
166
167	err = hwrng_register(&priv->timeriomem_rng_ops);
168	if (err) {
169		dev_err(&pdev->dev, "problem registering\n");
170		goto out_timer;
171	}
172
173	dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
174			priv->io_base, period);
175
176	return 0;
177
178out_timer:
179	del_timer_sync(&priv->timer);
180	return err;
181}
182
183static int timeriomem_rng_remove(struct platform_device *pdev)
184{
185	struct timeriomem_rng_private_data *priv = platform_get_drvdata(pdev);
186
187	hwrng_unregister(&priv->timeriomem_rng_ops);
188
189	del_timer_sync(&priv->timer);
190
191	return 0;
192}
193
194static const struct of_device_id timeriomem_rng_match[] = {
195	{ .compatible = "timeriomem_rng" },
196	{},
197};
198MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
199
200static struct platform_driver timeriomem_rng_driver = {
201	.driver = {
202		.name		= "timeriomem_rng",
203		.owner		= THIS_MODULE,
204		.of_match_table	= timeriomem_rng_match,
205	},
206	.probe		= timeriomem_rng_probe,
207	.remove		= timeriomem_rng_remove,
208};
209
210module_platform_driver(timeriomem_rng_driver);
211
212MODULE_LICENSE("GPL");
213MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
214MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
215