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
24struct atmel_trng {
25	struct clk *clk;
26	void __iomem *base;
27	struct hwrng rng;
28};
29
30static 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
51static 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
86err_register:
87	clk_disable(trng->clk);
88	return ret;
89}
90
91static 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
104static 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
113static 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
120static 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
126static const struct of_device_id atmel_trng_dt_ids[] = {
127	{ .compatible = "atmel,at91sam9g45-trng" },
128	{ /* sentinel */ }
129};
130MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
131
132static 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
144module_platform_driver(atmel_trng_driver);
145
146MODULE_LICENSE("GPL");
147MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
148MODULE_DESCRIPTION("Atmel true random number generator driver");
149