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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/completion.h>
24#include <linux/delay.h>
25#include <linux/hrtimer.h>
26#include <linux/hw_random.h>
27#include <linux/io.h>
28#include <linux/ktime.h>
29#include <linux/module.h>
30#include <linux/of.h>
31#include <linux/platform_device.h>
32#include <linux/slab.h>
33#include <linux/time.h>
34#include <linux/timeriomem-rng.h>
35
36struct timeriomem_rng_private {
37 void __iomem *io_base;
38 ktime_t period;
39 unsigned int present:1;
40
41 struct hrtimer timer;
42 struct completion completion;
43
44 struct hwrng rng_ops;
45};
46
47static int timeriomem_rng_read(struct hwrng *hwrng, void *data,
48 size_t max, bool wait)
49{
50 struct timeriomem_rng_private *priv =
51 container_of(hwrng, struct timeriomem_rng_private, rng_ops);
52 int retval = 0;
53 int period_us = ktime_to_us(priv->period);
54
55 /*
56 * There may not have been enough time for new data to be generated
57 * since the last request. If the caller doesn't want to wait, let them
58 * bail out. Otherwise, wait for the completion. If the new data has
59 * already been generated, the completion should already be available.
60 */
61 if (!wait && !priv->present)
62 return 0;
63
64 wait_for_completion(&priv->completion);
65
66 do {
67 /*
68 * After the first read, all additional reads will need to wait
69 * for the RNG to generate new data. Since the period can have
70 * a wide range of values (1us to 1s have been observed), allow
71 * for 1% tolerance in the sleep time rather than a fixed value.
72 */
73 if (retval > 0)
74 usleep_range(period_us,
75 period_us + min(1, period_us / 100));
76
77 *(u32 *)data = readl(priv->io_base);
78 retval += sizeof(u32);
79 data += sizeof(u32);
80 max -= sizeof(u32);
81 } while (wait && max > sizeof(u32));
82
83 /*
84 * Block any new callers until the RNG has had time to generate new
85 * data.
86 */
87 priv->present = 0;
88 reinit_completion(&priv->completion);
89 hrtimer_forward_now(&priv->timer, priv->period);
90 hrtimer_restart(&priv->timer);
91
92 return retval;
93}
94
95static enum hrtimer_restart timeriomem_rng_trigger(struct hrtimer *timer)
96{
97 struct timeriomem_rng_private *priv
98 = container_of(timer, struct timeriomem_rng_private, timer);
99
100 priv->present = 1;
101 complete(&priv->completion);
102
103 return HRTIMER_NORESTART;
104}
105
106static int timeriomem_rng_probe(struct platform_device *pdev)
107{
108 struct timeriomem_rng_data *pdata = pdev->dev.platform_data;
109 struct timeriomem_rng_private *priv;
110 struct resource *res;
111 int err = 0;
112 int period;
113
114 if (!pdev->dev.of_node && !pdata) {
115 dev_err(&pdev->dev, "timeriomem_rng_data is missing\n");
116 return -EINVAL;
117 }
118
119 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
120 if (!res)
121 return -ENXIO;
122
123 if (res->start % 4 != 0 || resource_size(res) != 4) {
124 dev_err(&pdev->dev,
125 "address must be four bytes wide and aligned\n");
126 return -EINVAL;
127 }
128
129 /* Allocate memory for the device structure (and zero it) */
130 priv = devm_kzalloc(&pdev->dev,
131 sizeof(struct timeriomem_rng_private), GFP_KERNEL);
132 if (!priv)
133 return -ENOMEM;
134
135 platform_set_drvdata(pdev, priv);
136
137 if (pdev->dev.of_node) {
138 int i;
139
140 if (!of_property_read_u32(pdev->dev.of_node,
141 "period", &i))
142 period = i;
143 else {
144 dev_err(&pdev->dev, "missing period\n");
145 return -EINVAL;
146 }
147
148 if (!of_property_read_u32(pdev->dev.of_node,
149 "quality", &i))
150 priv->rng_ops.quality = i;
151 else
152 priv->rng_ops.quality = 0;
153 } else {
154 period = pdata->period;
155 priv->rng_ops.quality = pdata->quality;
156 }
157
158 priv->period = ns_to_ktime(period * NSEC_PER_USEC);
159 init_completion(&priv->completion);
160 hrtimer_init(&priv->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
161 priv->timer.function = timeriomem_rng_trigger;
162
163 priv->rng_ops.name = dev_name(&pdev->dev);
164 priv->rng_ops.read = timeriomem_rng_read;
165
166 priv->io_base = devm_ioremap_resource(&pdev->dev, res);
167 if (IS_ERR(priv->io_base)) {
168 return PTR_ERR(priv->io_base);
169 }
170
171 /* Assume random data is already available. */
172 priv->present = 1;
173 complete(&priv->completion);
174
175 err = hwrng_register(&priv->rng_ops);
176 if (err) {
177 dev_err(&pdev->dev, "problem registering\n");
178 return err;
179 }
180
181 dev_info(&pdev->dev, "32bits from 0x%p @ %dus\n",
182 priv->io_base, period);
183
184 return 0;
185}
186
187static int timeriomem_rng_remove(struct platform_device *pdev)
188{
189 struct timeriomem_rng_private *priv = platform_get_drvdata(pdev);
190
191 hwrng_unregister(&priv->rng_ops);
192 hrtimer_cancel(&priv->timer);
193
194 return 0;
195}
196
197static const struct of_device_id timeriomem_rng_match[] = {
198 { .compatible = "timeriomem_rng" },
199 {},
200};
201MODULE_DEVICE_TABLE(of, timeriomem_rng_match);
202
203static struct platform_driver timeriomem_rng_driver = {
204 .driver = {
205 .name = "timeriomem_rng",
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");