1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2010-2012 Broadcom. All rights reserved.
4  * Copyright (c) 2013 Lubomir Rintel
5  */
6 
7 #include <linux/hw_random.h>
8 #include <linux/io.h>
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/of.h>
12 #include <linux/platform_device.h>
13 #include <linux/printk.h>
14 #include <linux/clk.h>
15 #include <linux/reset.h>
16 
17 #define RNG_CTRL	0x0
18 #define RNG_STATUS	0x4
19 #define RNG_DATA	0x8
20 #define RNG_INT_MASK	0x10
21 
22 /* enable rng */
23 #define RNG_RBGEN	0x1
24 
25 /* the initial numbers generated are "less random" so will be discarded */
26 #define RNG_WARMUP_COUNT 0x40000
27 
28 #define RNG_INT_OFF	0x1
29 
30 struct bcm2835_rng_priv {
31 	struct hwrng rng;
32 	void __iomem *base;
33 	bool mask_interrupts;
34 	struct clk *clk;
35 	struct reset_control *reset;
36 };
37 
38 static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
39 {
40 	return container_of(rng, struct bcm2835_rng_priv, rng);
41 }
42 
43 static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
44 {
45 	/* MIPS chips strapped for BE will automagically configure the
46 	 * peripheral registers for CPU-native byte order.
47 	 */
48 	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
49 		return __raw_readl(priv->base + offset);
50 	else
51 		return readl(priv->base + offset);
52 }
53 
54 static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
55 			      u32 offset)
56 {
57 	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
58 		__raw_writel(val, priv->base + offset);
59 	else
60 		writel(val, priv->base + offset);
61 }
62 
63 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
64 			       bool wait)
65 {
66 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
67 	u32 max_words = max / sizeof(u32);
68 	u32 num_words, count;
69 
70 	while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
71 		if (!wait)
72 			return 0;
73 		hwrng_msleep(rng, 1000);
74 	}
75 
76 	num_words = rng_readl(priv, RNG_STATUS) >> 24;
77 	if (num_words > max_words)
78 		num_words = max_words;
79 
80 	for (count = 0; count < num_words; count++)
81 		((u32 *)buf)[count] = rng_readl(priv, RNG_DATA);
82 
83 	return num_words * sizeof(u32);
84 }
85 
86 static int bcm2835_rng_init(struct hwrng *rng)
87 {
88 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
89 	int ret = 0;
90 	u32 val;
91 
92 	ret = clk_prepare_enable(priv->clk);
93 	if (ret)
94 		return ret;
95 
96 	ret = reset_control_reset(priv->reset);
97 	if (ret)
98 		return ret;
99 
100 	if (priv->mask_interrupts) {
101 		/* mask the interrupt */
102 		val = rng_readl(priv, RNG_INT_MASK);
103 		val |= RNG_INT_OFF;
104 		rng_writel(priv, val, RNG_INT_MASK);
105 	}
106 
107 	/* set warm-up count & enable */
108 	rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
109 	rng_writel(priv, RNG_RBGEN, RNG_CTRL);
110 
111 	return ret;
112 }
113 
114 static void bcm2835_rng_cleanup(struct hwrng *rng)
115 {
116 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
117 
118 	/* disable rng hardware */
119 	rng_writel(priv, 0, RNG_CTRL);
120 
121 	clk_disable_unprepare(priv->clk);
122 }
123 
124 struct bcm2835_rng_of_data {
125 	bool mask_interrupts;
126 };
127 
128 static const struct bcm2835_rng_of_data nsp_rng_of_data = {
129 	.mask_interrupts = true,
130 };
131 
132 static const struct of_device_id bcm2835_rng_of_match[] = {
133 	{ .compatible = "brcm,bcm2835-rng"},
134 	{ .compatible = "brcm,bcm-nsp-rng", .data = &nsp_rng_of_data },
135 	{ .compatible = "brcm,bcm5301x-rng", .data = &nsp_rng_of_data },
136 	{ .compatible = "brcm,bcm6368-rng"},
137 	{},
138 };
139 
140 static int bcm2835_rng_probe(struct platform_device *pdev)
141 {
142 	const struct bcm2835_rng_of_data *of_data;
143 	struct device *dev = &pdev->dev;
144 	const struct of_device_id *rng_id;
145 	struct bcm2835_rng_priv *priv;
146 	int err;
147 
148 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
149 	if (!priv)
150 		return -ENOMEM;
151 
152 	platform_set_drvdata(pdev, priv);
153 
154 	/* map peripheral */
155 	priv->base = devm_platform_ioremap_resource(pdev, 0);
156 	if (IS_ERR(priv->base))
157 		return PTR_ERR(priv->base);
158 
159 	/* Clock is optional on most platforms */
160 	priv->clk = devm_clk_get_optional(dev, NULL);
161 	if (IS_ERR(priv->clk))
162 		return PTR_ERR(priv->clk);
163 
164 	priv->reset = devm_reset_control_get_optional_exclusive(dev, NULL);
165 	if (IS_ERR(priv->reset))
166 		return PTR_ERR(priv->reset);
167 
168 	priv->rng.name = pdev->name;
169 	priv->rng.init = bcm2835_rng_init;
170 	priv->rng.read = bcm2835_rng_read;
171 	priv->rng.cleanup = bcm2835_rng_cleanup;
172 
173 	if (dev_of_node(dev)) {
174 		rng_id = of_match_node(bcm2835_rng_of_match, dev->of_node);
175 		if (!rng_id)
176 			return -EINVAL;
177 
178 		/* Check for rng init function, execute it */
179 		of_data = rng_id->data;
180 		if (of_data)
181 			priv->mask_interrupts = of_data->mask_interrupts;
182 	}
183 
184 	/* register driver */
185 	err = devm_hwrng_register(dev, &priv->rng);
186 	if (err)
187 		dev_err(dev, "hwrng registration failed\n");
188 	else
189 		dev_info(dev, "hwrng registered\n");
190 
191 	return err;
192 }
193 
194 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
195 
196 static const struct platform_device_id bcm2835_rng_devtype[] = {
197 	{ .name = "bcm2835-rng" },
198 	{ .name = "bcm63xx-rng" },
199 	{ /* sentinel */ }
200 };
201 MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
202 
203 static struct platform_driver bcm2835_rng_driver = {
204 	.driver = {
205 		.name = "bcm2835-rng",
206 		.of_match_table = bcm2835_rng_of_match,
207 	},
208 	.probe		= bcm2835_rng_probe,
209 	.id_table	= bcm2835_rng_devtype,
210 };
211 module_platform_driver(bcm2835_rng_driver);
212 
213 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
214 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
215 MODULE_LICENSE("GPL v2");
216