1 /*
2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
3 *
4 * This file is licensed under the terms of the GNU General Public
5 * License version 2. This program is licensed "as is" without any
6 * warranty of any kind, whether express or implied.
7 */
8
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/mod_devicetable.h>
12 #include <linux/slab.h>
13 #include <linux/err.h>
14 #include <linux/clk.h>
15 #include <linux/io.h>
16 #include <linux/hw_random.h>
17 #include <linux/platform_device.h>
18
19 #define TRNG_CR 0x00
20 #define TRNG_ISR 0x1c
21 #define TRNG_ODATA 0x50
22
23 #define TRNG_KEY 0x524e4700 /* RNG */
24
25 struct atmel_trng {
26 struct clk *clk;
27 void __iomem *base;
28 struct hwrng rng;
29 };
30
atmel_trng_read(struct hwrng * rng,void * buf,size_t max,bool wait)31 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
32 bool wait)
33 {
34 struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
35 u32 *data = buf;
36
37 /* data ready? */
38 if (readl(trng->base + TRNG_ISR) & 1) {
39 *data = readl(trng->base + TRNG_ODATA);
40 /*
41 ensure data ready is only set again AFTER the next data
42 word is ready in case it got set between checking ISR
43 and reading ODATA, so we don't risk re-reading the
44 same word
45 */
46 readl(trng->base + TRNG_ISR);
47 return 4;
48 } else
49 return 0;
50 }
51
atmel_trng_enable(struct atmel_trng * trng)52 static void atmel_trng_enable(struct atmel_trng *trng)
53 {
54 writel(TRNG_KEY | 1, trng->base + TRNG_CR);
55 }
56
atmel_trng_disable(struct atmel_trng * trng)57 static void atmel_trng_disable(struct atmel_trng *trng)
58 {
59 writel(TRNG_KEY, trng->base + TRNG_CR);
60 }
61
atmel_trng_probe(struct platform_device * pdev)62 static int atmel_trng_probe(struct platform_device *pdev)
63 {
64 struct atmel_trng *trng;
65 struct resource *res;
66 int ret;
67
68 trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
69 if (!trng)
70 return -ENOMEM;
71
72 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
73 trng->base = devm_ioremap_resource(&pdev->dev, res);
74 if (IS_ERR(trng->base))
75 return PTR_ERR(trng->base);
76
77 trng->clk = devm_clk_get(&pdev->dev, NULL);
78 if (IS_ERR(trng->clk))
79 return PTR_ERR(trng->clk);
80
81 ret = clk_prepare_enable(trng->clk);
82 if (ret)
83 return ret;
84
85 atmel_trng_enable(trng);
86 trng->rng.name = pdev->name;
87 trng->rng.read = atmel_trng_read;
88
89 ret = devm_hwrng_register(&pdev->dev, &trng->rng);
90 if (ret)
91 goto err_register;
92
93 platform_set_drvdata(pdev, trng);
94
95 return 0;
96
97 err_register:
98 clk_disable_unprepare(trng->clk);
99 return ret;
100 }
101
atmel_trng_remove(struct platform_device * pdev)102 static int atmel_trng_remove(struct platform_device *pdev)
103 {
104 struct atmel_trng *trng = platform_get_drvdata(pdev);
105
106
107 atmel_trng_disable(trng);
108 clk_disable_unprepare(trng->clk);
109
110 return 0;
111 }
112
113 #ifdef CONFIG_PM
atmel_trng_suspend(struct device * dev)114 static int atmel_trng_suspend(struct device *dev)
115 {
116 struct atmel_trng *trng = dev_get_drvdata(dev);
117
118 atmel_trng_disable(trng);
119 clk_disable_unprepare(trng->clk);
120
121 return 0;
122 }
123
atmel_trng_resume(struct device * dev)124 static int atmel_trng_resume(struct device *dev)
125 {
126 struct atmel_trng *trng = dev_get_drvdata(dev);
127 int ret;
128
129 ret = clk_prepare_enable(trng->clk);
130 if (ret)
131 return ret;
132
133 atmel_trng_enable(trng);
134
135 return 0;
136 }
137
138 static const struct dev_pm_ops atmel_trng_pm_ops = {
139 .suspend = atmel_trng_suspend,
140 .resume = atmel_trng_resume,
141 };
142 #endif /* CONFIG_PM */
143
144 static const struct of_device_id atmel_trng_dt_ids[] = {
145 { .compatible = "atmel,at91sam9g45-trng" },
146 { /* sentinel */ }
147 };
148 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
149
150 static struct platform_driver atmel_trng_driver = {
151 .probe = atmel_trng_probe,
152 .remove = atmel_trng_remove,
153 .driver = {
154 .name = "atmel-trng",
155 #ifdef CONFIG_PM
156 .pm = &atmel_trng_pm_ops,
157 #endif /* CONFIG_PM */
158 .of_match_table = atmel_trng_dt_ids,
159 },
160 };
161
162 module_platform_driver(atmel_trng_driver);
163
164 MODULE_LICENSE("GPL");
165 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
166 MODULE_DESCRIPTION("Atmel true random number generator driver");
167