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/slab.h>
12 #include <linux/err.h>
13 #include <linux/clk.h>
14 #include <linux/io.h>
15 #include <linux/hw_random.h>
16 #include <linux/platform_device.h>
17 
18 #define TRNG_CR		0x00
19 #define TRNG_ISR	0x1c
20 #define TRNG_ODATA	0x50
21 
22 #define TRNG_KEY	0x524e4700 /* RNG */
23 
24 struct atmel_trng {
25 	struct clk *clk;
26 	void __iomem *base;
27 	struct hwrng rng;
28 };
29 
30 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
31 			   bool wait)
32 {
33 	struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
34 	u32 *data = buf;
35 
36 	/* data ready? */
37 	if (readl(trng->base + TRNG_ISR) & 1) {
38 		*data = readl(trng->base + TRNG_ODATA);
39 		/*
40 		  ensure data ready is only set again AFTER the next data
41 		  word is ready in case it got set between checking ISR
42 		  and reading ODATA, so we don't risk re-reading the
43 		  same word
44 		*/
45 		readl(trng->base + TRNG_ISR);
46 		return 4;
47 	} else
48 		return 0;
49 }
50 
51 static int atmel_trng_probe(struct platform_device *pdev)
52 {
53 	struct atmel_trng *trng;
54 	struct resource *res;
55 	int ret;
56 
57 	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
58 	if (!trng)
59 		return -ENOMEM;
60 
61 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
62 	trng->base = devm_ioremap_resource(&pdev->dev, res);
63 	if (IS_ERR(trng->base))
64 		return PTR_ERR(trng->base);
65 
66 	trng->clk = devm_clk_get(&pdev->dev, NULL);
67 	if (IS_ERR(trng->clk))
68 		return PTR_ERR(trng->clk);
69 
70 	ret = clk_prepare_enable(trng->clk);
71 	if (ret)
72 		return ret;
73 
74 	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
75 	trng->rng.name = pdev->name;
76 	trng->rng.read = atmel_trng_read;
77 
78 	ret = hwrng_register(&trng->rng);
79 	if (ret)
80 		goto err_register;
81 
82 	platform_set_drvdata(pdev, trng);
83 
84 	return 0;
85 
86 err_register:
87 	clk_disable(trng->clk);
88 	return ret;
89 }
90 
91 static int atmel_trng_remove(struct platform_device *pdev)
92 {
93 	struct atmel_trng *trng = platform_get_drvdata(pdev);
94 
95 	hwrng_unregister(&trng->rng);
96 
97 	writel(TRNG_KEY, trng->base + TRNG_CR);
98 	clk_disable_unprepare(trng->clk);
99 
100 	return 0;
101 }
102 
103 #ifdef CONFIG_PM
104 static int atmel_trng_suspend(struct device *dev)
105 {
106 	struct atmel_trng *trng = dev_get_drvdata(dev);
107 
108 	clk_disable_unprepare(trng->clk);
109 
110 	return 0;
111 }
112 
113 static int atmel_trng_resume(struct device *dev)
114 {
115 	struct atmel_trng *trng = dev_get_drvdata(dev);
116 
117 	return clk_prepare_enable(trng->clk);
118 }
119 
120 static const struct dev_pm_ops atmel_trng_pm_ops = {
121 	.suspend	= atmel_trng_suspend,
122 	.resume		= atmel_trng_resume,
123 };
124 #endif /* CONFIG_PM */
125 
126 static const struct of_device_id atmel_trng_dt_ids[] = {
127 	{ .compatible = "atmel,at91sam9g45-trng" },
128 	{ /* sentinel */ }
129 };
130 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
131 
132 static struct platform_driver atmel_trng_driver = {
133 	.probe		= atmel_trng_probe,
134 	.remove		= atmel_trng_remove,
135 	.driver		= {
136 		.name	= "atmel-trng",
137 #ifdef CONFIG_PM
138 		.pm	= &atmel_trng_pm_ops,
139 #endif /* CONFIG_PM */
140 		.of_match_table = atmel_trng_dt_ids,
141 	},
142 };
143 
144 module_platform_driver(atmel_trng_driver);
145 
146 MODULE_LICENSE("GPL");
147 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
148 MODULE_DESCRIPTION("Atmel true random number generator driver");
149