1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2016 HiSilicon Co., Ltd.
4  */
5 
6 #include <linux/err.h>
7 #include <linux/kernel.h>
8 #include <linux/hw_random.h>
9 #include <linux/io.h>
10 #include <linux/module.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13 #include <linux/random.h>
14 
15 #define RNG_SEED	0x0
16 #define RNG_CTRL	0x4
17   #define RNG_SEED_SEL	BIT(2)
18   #define RNG_RING_EN	BIT(1)
19   #define RNG_EN	BIT(0)
20 #define RNG_RAN_NUM	0x10
21 #define RNG_PHY_SEED	0x14
22 
23 #define to_hisi_rng(p)	container_of(p, struct hisi_rng, rng)
24 
25 static int seed_sel;
26 module_param(seed_sel, int, S_IRUGO);
27 MODULE_PARM_DESC(seed_sel, "Auto reload seed. 0, use LFSR(default); 1, use ring oscillator.");
28 
29 struct hisi_rng {
30 	void __iomem *base;
31 	struct hwrng rng;
32 };
33 
34 static int hisi_rng_init(struct hwrng *rng)
35 {
36 	struct hisi_rng *hrng = to_hisi_rng(rng);
37 	int val = RNG_EN;
38 	u32 seed;
39 
40 	/* get a random number as initial seed */
41 	get_random_bytes(&seed, sizeof(seed));
42 
43 	writel_relaxed(seed, hrng->base + RNG_SEED);
44 
45 	/**
46 	 * The seed is reload periodically, there are two choice
47 	 * of seeds, default seed using the value from LFSR, or
48 	 * will use seed generated by ring oscillator.
49 	 */
50 	if (seed_sel == 1)
51 		val |= RNG_RING_EN | RNG_SEED_SEL;
52 
53 	writel_relaxed(val, hrng->base + RNG_CTRL);
54 	return 0;
55 }
56 
57 static void hisi_rng_cleanup(struct hwrng *rng)
58 {
59 	struct hisi_rng *hrng = to_hisi_rng(rng);
60 
61 	writel_relaxed(0, hrng->base + RNG_CTRL);
62 }
63 
64 static int hisi_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
65 {
66 	struct hisi_rng *hrng = to_hisi_rng(rng);
67 	u32 *data = buf;
68 
69 	*data = readl_relaxed(hrng->base + RNG_RAN_NUM);
70 	return 4;
71 }
72 
73 static int hisi_rng_probe(struct platform_device *pdev)
74 {
75 	struct hisi_rng *rng;
76 	int ret;
77 
78 	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
79 	if (!rng)
80 		return -ENOMEM;
81 
82 	platform_set_drvdata(pdev, rng);
83 
84 	rng->base = devm_platform_ioremap_resource(pdev, 0);
85 	if (IS_ERR(rng->base))
86 		return PTR_ERR(rng->base);
87 
88 	rng->rng.name = pdev->name;
89 	rng->rng.init = hisi_rng_init;
90 	rng->rng.cleanup = hisi_rng_cleanup;
91 	rng->rng.read = hisi_rng_read;
92 
93 	ret = devm_hwrng_register(&pdev->dev, &rng->rng);
94 	if (ret) {
95 		dev_err(&pdev->dev, "failed to register hwrng\n");
96 		return ret;
97 	}
98 
99 	return 0;
100 }
101 
102 static const struct of_device_id hisi_rng_dt_ids[] __maybe_unused = {
103 	{ .compatible = "hisilicon,hip04-rng" },
104 	{ .compatible = "hisilicon,hip05-rng" },
105 	{ }
106 };
107 MODULE_DEVICE_TABLE(of, hisi_rng_dt_ids);
108 
109 static struct platform_driver hisi_rng_driver = {
110 	.probe		= hisi_rng_probe,
111 	.driver		= {
112 		.name	= "hisi-rng",
113 		.of_match_table = of_match_ptr(hisi_rng_dt_ids),
114 	},
115 };
116 
117 module_platform_driver(hisi_rng_driver);
118 
119 MODULE_LICENSE("GPL");
120 MODULE_AUTHOR("Kefeng Wang <wangkefeng.wang@huawei>");
121 MODULE_DESCRIPTION("Hisilicon random number generator driver");
122