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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
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
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 .of_match_table = timeriomem_rng_match,
204 },
205 .probe = timeriomem_rng_probe,
206 .remove = timeriomem_rng_remove,
207};
208
209module_platform_driver(timeriomem_rng_driver);
210
211MODULE_LICENSE("GPL");
212MODULE_AUTHOR("Alexander Clouter <alex@digriz.org.uk>");
213MODULE_DESCRIPTION("Timer IOMEM H/W RNG driver");
214
