1 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
2 /*
3  * Copyright (c) 2016 BayLibre, SAS.
4  * Author: Neil Armstrong <narmstrong@baylibre.com>
5  * Copyright (C) 2014 Amlogic, Inc.
6  */
7 #include <linux/err.h>
8 #include <linux/module.h>
9 #include <linux/io.h>
10 #include <linux/platform_device.h>
11 #include <linux/hw_random.h>
12 #include <linux/slab.h>
13 #include <linux/types.h>
14 #include <linux/of.h>
15 #include <linux/clk.h>
16 
17 #define RNG_DATA 0x00
18 
19 struct meson_rng_data {
20 	void __iomem *base;
21 	struct platform_device *pdev;
22 	struct hwrng rng;
23 	struct clk *core_clk;
24 };
25 
26 static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
27 {
28 	struct meson_rng_data *data =
29 			container_of(rng, struct meson_rng_data, rng);
30 
31 	*(u32 *)buf = readl_relaxed(data->base + RNG_DATA);
32 
33 	return sizeof(u32);
34 }
35 
36 static void meson_rng_clk_disable(void *data)
37 {
38 	clk_disable_unprepare(data);
39 }
40 
41 static int meson_rng_probe(struct platform_device *pdev)
42 {
43 	struct device *dev = &pdev->dev;
44 	struct meson_rng_data *data;
45 	struct resource *res;
46 	int ret;
47 
48 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
49 	if (!data)
50 		return -ENOMEM;
51 
52 	data->pdev = pdev;
53 
54 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
55 	data->base = devm_ioremap_resource(dev, res);
56 	if (IS_ERR(data->base))
57 		return PTR_ERR(data->base);
58 
59 	data->core_clk = devm_clk_get(dev, "core");
60 	if (IS_ERR(data->core_clk))
61 		data->core_clk = NULL;
62 
63 	if (data->core_clk) {
64 		ret = clk_prepare_enable(data->core_clk);
65 		if (ret)
66 			return ret;
67 		ret = devm_add_action_or_reset(dev, meson_rng_clk_disable,
68 					       data->core_clk);
69 		if (ret)
70 			return ret;
71 	}
72 
73 	data->rng.name = pdev->name;
74 	data->rng.read = meson_rng_read;
75 
76 	platform_set_drvdata(pdev, data);
77 
78 	return devm_hwrng_register(dev, &data->rng);
79 }
80 
81 static const struct of_device_id meson_rng_of_match[] = {
82 	{ .compatible = "amlogic,meson-rng", },
83 	{},
84 };
85 MODULE_DEVICE_TABLE(of, meson_rng_of_match);
86 
87 static struct platform_driver meson_rng_driver = {
88 	.probe	= meson_rng_probe,
89 	.driver	= {
90 		.name = "meson-rng",
91 		.of_match_table = meson_rng_of_match,
92 	},
93 };
94 
95 module_platform_driver(meson_rng_driver);
96 
97 MODULE_DESCRIPTION("Meson H/W Random Number Generator driver");
98 MODULE_AUTHOR("Lawrence Mok <lawrence.mok@amlogic.com>");
99 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
100 MODULE_LICENSE("Dual BSD/GPL");
101