Loading...
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * drivers/char/hw_random/timeriomem-rng.c
4 *
5 * Copyright (C) 2009 Alexander Clouter <alex@digriz.org.uk>
6 *
7 * Derived from drivers/char/hw_random/omap-rng.c
8 * Copyright 2005 (c) MontaVista Software, Inc.
9 * Author: Deepak Saxena <dsaxena@plexity.net>
10 *
11 * Overview:
12 * This driver is useful for platforms that have an IO range that provides
13 * periodic random data from a single IO memory address. All the platform
14 * has to do is provide the address and 'wait time' that new data becomes
15 * available.
16 *
17 * TODO: add support for reading sizes other than 32bits and masking
18 */
19
20#include <linux/completion.h>
21#include <linux/delay.h>
22#include <linux/hrtimer.h>
23#include <linux/hw_random.h>
24#include <linux/io.h>
25#include <linux/ktime.h>
26#include <linux/module.h>
27#include <linux/of.h>
28#include <linux/platform_device.h>
29#include <linux/slab.h>
30#include <linux/time.h>
31#include <linux/timeriomem-rng.h>
32
33struct timeriomem_rng_private {
34 void __iomem *io_base;
35 ktime_t period;
36 unsigned int present:1;
37
38 struct hrtimer timer;
39 struct completion completion;
40
41 struct hwrng rng_ops;
42};
43
44static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
45 size_t max, bool wait)
46{
47 struct timeriomem_rng_private *priv =
48 container_of(hwrng, struct timeriomem_rng_private, rng_ops);
49 int retval = 0;
50 int period_us = ktime_to_us(priv->period);
51
52 /*
53 * There may not have been enough time for new data to be generated
54 * since the last request. If the caller doesn't want to wait, let them
55 * bail out. Otherwise, wait for the completion. If the new data has
56 * already been generated, the completion should already be available.
57 */
58 if (!wait && !priv->present)
59 return 0;
60
61 wait_for_completion(&priv->completion);
62
63 do {
64 /*
65 * After the first read, all additional reads will need to wait
66 * for the RNG to generate new data. Since the period can have
67 * a wide range of values (1us to 1s have been observed), allow
68 * for 1% tolerance in the sleep time rather than a fixed value.
69 */
70 if (retval > 0)
71 usleep_range(period_us,
72 period_us + max(1, period_us / 100));
73
74 *(u32 *)data = readl(priv->io_base);
75 retval += sizeof(u32);
76 data += sizeof(u32);
77 max -= sizeof(u32);
78 } while (wait && max > sizeof(u32));
79
80 /*
81 * Block any new callers until the RNG has had time to generate new
82 * data.
83 */
84 priv->present = 0;
85 reinit_completion(&priv->completion);
86 hrtimer_forward_now(&priv->timer, priv->period);
87 hrtimer_restart(&priv->timer);
88
89 return retval;
90}
91
92static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
93{
94 struct timeriomem_rng_private *priv
95 = container_of(timer, struct timeriomem_rng_private, timer);
96
97 priv->present = 1;
98 complete(&priv->completion);
99
100 return HRTIMER_NORESTART;
101}
102
103static int timeriomem_rng_probe(struct platform_device *pdev)
104{
105 struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
106 struct timeriomem_rng_private *priv;
107 struct resource *res;
108 int err = 0;
109 int period;
110
111 if (!pdev->dev.of_node && !pdata) {
112 dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
113 return -EINVAL;
114 }
115
116 /* Allocate memory for the device structure (and zero it) */
117 priv = devm_kzalloc(&pdev->dev,
118 sizeof(struct timeriomem_rng_private), GFP_KERNEL);
119 if (!priv)
120 return -ENOMEM;
121
122 platform_set_drvdata(pdev, priv);
123
124 priv->io_base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
125 if (IS_ERR(priv->io_base))
126 return PTR_ERR(priv->io_base);
127
128 if (res->start % 4 != 0 || resource_size(res) < 4) {
129 dev_err(&pdev->dev,
130 "address must be at least four bytes wide and 32-bit aligned\n");
131 return -EINVAL;
132 }
133
134 if (pdev->dev.of_node) {
135 int i;
136
137 if (!of_property_read_u32(pdev->dev.of_node,
138 "period", &i))
139 period = i;
140 else {
141 dev_err(&pdev->dev, "missing period\n");
142 return -EINVAL;
143 }
144
145 if (!of_property_read_u32(pdev->dev.of_node,
146 "quality", &i))
147 priv->rng_ops.quality = i;
148 } else {
149 period = pdata->period;
150 priv->rng_ops.quality = pdata->quality;
151 }
152
153 priv->period = ns_to_ktime(period * NSEC_PER_USEC);
154 init_completion(&priv->completion);
155 hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
156 priv->timer.function = timeriomem_rng_trigger;
157
158 priv->rng_ops.name = dev_name(&pdev->dev);
159 priv->rng_ops.read = timeriomem_rng_read;
160
161 /* Assume random data is already available. */
162 priv->present = 1;
163 complete(&priv->completion);
164
165 err = devm_hwrng_register(&pdev->dev, &priv->rng_ops);
166 if (err) {
167 dev_err(&pdev->dev, "problem registering\n");
168 return err;
169 }
170
171 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
172 priv->io_base, period);
173
174 return 0;
175}
176
177static void timeriomem_rng_remove(struct platform_device *pdev)
178{
179 struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
180
181 hrtimer_cancel(&priv->timer);
182}
183
184static const struct of_device_id timeriomem_rng_match[] = {
185 { .compatible = "timeriomem_rng" },
186 {},
187};
188MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
189
190static struct platform_driver timeriomem_rng_driver = {
191 .driver = {
192 .name = "timeriomem_rng",
193 .of_match_table = timeriomem_rng_match,
194 },
195 .probe = timeriomem_rng_probe,
196 .remove_new = timeriomem_rng_remove,
197};
198
199module_platform_driver(timeriomem_rng_driver);
200
201MODULE_LICENSE("GPL");
202MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
203MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
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
34static struct timeriomem_rng_data *timeriomem_rng_data;
35
36static void timeriomem_rng_trigger(unsigned long);
37static 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 */
42static 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
55static 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
78static void timeriomem_rng_trigger(unsigned long dummy)
79{
80 timeriomem_rng_data->present = 1;
81 complete(&timeriomem_rng_data->completion);
82}
83
84static 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
91static 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, resource_size(res));
104 if (!timeriomem_rng_data->address)
105 return -EIO;
106
107 if (timeriomem_rng_data->period != 0
108 && usecs_to_jiffies(timeriomem_rng_data->period) > 0) {
109 timeriomem_rng_timer.expires = jiffies;
110
111 timeriomem_rng_ops.priv = usecs_to_jiffies(
112 timeriomem_rng_data->period);
113 }
114 timeriomem_rng_data->present = 1;
115
116 ret = hwrng_register(&timeriomem_rng_ops);
117 if (ret)
118 goto failed;
119
120 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
121 timeriomem_rng_data->address,
122 timeriomem_rng_data->period);
123
124 return 0;
125
126failed:
127 dev_err(&pdev->dev, "problem registering\n");
128 iounmap(timeriomem_rng_data->address);
129
130 return ret;
131}
132
133static int __devexit timeriomem_rng_remove(struct platform_device *pdev)
134{
135 del_timer_sync(&timeriomem_rng_timer);
136 hwrng_unregister(&timeriomem_rng_ops);
137
138 iounmap(timeriomem_rng_data->address);
139
140 return 0;
141}
142
143static struct platform_driver timeriomem_rng_driver = {
144 .driver = {
145 .name = "timeriomem_rng",
146 .owner = THIS_MODULE,
147 },
148 .probe = timeriomem_rng_probe,
149 .remove = __devexit_p(timeriomem_rng_remove),
150};
151
152static int __init timeriomem_rng_init(void)
153{
154 return platform_driver_register(&timeriomem_rng_driver);
155}
156
157static void __exit timeriomem_rng_exit(void)
158{
159 platform_driver_unregister(&timeriomem_rng_driver);
160}
161
162module_init(timeriomem_rng_init);
163module_exit(timeriomem_rng_exit);
164
165MODULE_LICENSE("GPL");
166MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
167MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");