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 void atmel_trng_enable(struct atmel_trng *trng)
52 {
53 	writel(TRNG_KEY | 1, trng->base + TRNG_CR);
54 }
55 
56 static void atmel_trng_disable(struct atmel_trng *trng)
57 {
58 	writel(TRNG_KEY, trng->base + TRNG_CR);
59 }
60 
61 static int atmel_trng_probe(struct platform_device *pdev)
62 {
63 	struct atmel_trng *trng;
64 	struct resource *res;
65 	int ret;
66 
67 	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
68 	if (!trng)
69 		return -ENOMEM;
70 
71 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
72 	trng->base = devm_ioremap_resource(&pdev->dev, res);
73 	if (IS_ERR(trng->base))
74 		return PTR_ERR(trng->base);
75 
76 	trng->clk = devm_clk_get(&pdev->dev, NULL);
77 	if (IS_ERR(trng->clk))
78 		return PTR_ERR(trng->clk);
79 
80 	ret = clk_prepare_enable(trng->clk);
81 	if (ret)
82 		return ret;
83 
84 	atmel_trng_enable(trng);
85 	trng->rng.name = pdev->name;
86 	trng->rng.read = atmel_trng_read;
87 
88 	ret = hwrng_register(&trng->rng);
89 	if (ret)
90 		goto err_register;
91 
92 	platform_set_drvdata(pdev, trng);
93 
94 	return 0;
95 
96 err_register:
97 	clk_disable_unprepare(trng->clk);
98 	return ret;
99 }
100 
101 static int atmel_trng_remove(struct platform_device *pdev)
102 {
103 	struct atmel_trng *trng = platform_get_drvdata(pdev);
104 
105 	hwrng_unregister(&trng->rng);
106 
107 	atmel_trng_disable(trng);
108 	clk_disable_unprepare(trng->clk);
109 
110 	return 0;
111 }
112 
113 #ifdef CONFIG_PM
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 
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