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_address.h>
12 #include <linux/of_platform.h>
13 #include <linux/platform_device.h>
14 #include <linux/printk.h>
15 #include <linux/clk.h>
16 #include <linux/reset.h>
17 
18 #define RNG_CTRL	0x0
19 #define RNG_STATUS	0x4
20 #define RNG_DATA	0x8
21 #define RNG_INT_MASK	0x10
22 
23 /* enable rng */
24 #define RNG_RBGEN	0x1
25 
26 /* the initial numbers generated are "less random" so will be discarded */
27 #define RNG_WARMUP_COUNT 0x40000
28 
29 #define RNG_INT_OFF	0x1
30 
31 struct bcm2835_rng_priv {
32 	struct hwrng rng;
33 	void __iomem *base;
34 	bool mask_interrupts;
35 	struct clk *clk;
36 	struct reset_control *reset;
37 };
38 
39 static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
40 {
41 	return container_of(rng, struct bcm2835_rng_priv, rng);
42 }
43 
44 static inline u32 rng_readl(struct bcm2835_rng_priv *priv, u32 offset)
45 {
46 	/* MIPS chips strapped for BE will automagically configure the
47 	 * peripheral registers for CPU-native byte order.
48 	 */
49 	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
50 		return __raw_readl(priv->base + offset);
51 	else
52 		return readl(priv->base + offset);
53 }
54 
55 static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val,
56 			      u32 offset)
57 {
58 	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
59 		__raw_writel(val, priv->base + offset);
60 	else
61 		writel(val, priv->base + offset);
62 }
63 
64 static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
65 			       bool wait)
66 {
67 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
68 	u32 max_words = max / sizeof(u32);
69 	u32 num_words, count;
70 
71 	while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) {
72 		if (!wait)
73 			return 0;
74 		hwrng_msleep(rng, 1000);
75 	}
76 
77 	num_words = rng_readl(priv, RNG_STATUS) >> 24;
78 	if (num_words > max_words)
79 		num_words = max_words;
80 
81 	for (count = 0; count < num_words; count++)
82 		((u32 *)buf)[count] = rng_readl(priv, RNG_DATA);
83 
84 	return num_words * sizeof(u32);
85 }
86 
87 static int bcm2835_rng_init(struct hwrng *rng)
88 {
89 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
90 	int ret = 0;
91 	u32 val;
92 
93 	ret = clk_prepare_enable(priv->clk);
94 	if (ret)
95 		return ret;
96 
97 	ret = reset_control_reset(priv->reset);
98 	if (ret)
99 		return ret;
100 
101 	if (priv->mask_interrupts) {
102 		/* mask the interrupt */
103 		val = rng_readl(priv, RNG_INT_MASK);
104 		val |= RNG_INT_OFF;
105 		rng_writel(priv, val, RNG_INT_MASK);
106 	}
107 
108 	/* set warm-up count & enable */
109 	rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS);
110 	rng_writel(priv, RNG_RBGEN, RNG_CTRL);
111 
112 	return ret;
113 }
114 
115 static void bcm2835_rng_cleanup(struct hwrng *rng)
116 {
117 	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
118 
119 	/* disable rng hardware */
120 	rng_writel(priv, 0, RNG_CTRL);
121 
122 	clk_disable_unprepare(priv->clk);
123 }
124 
125 struct bcm2835_rng_of_data {
126 	bool mask_interrupts;
127 };
128 
129 static const struct bcm2835_rng_of_data nsp_rng_of_data = {
130 	.mask_interrupts = true,
131 };
132 
133 static const struct of_device_id bcm2835_rng_of_match[] = {
134 	{ .compatible = "brcm,bcm2835-rng"},
135 	{ .compatible = "brcm,bcm-nsp-rng", .data = &nsp_rng_of_data },
136 	{ .compatible = "brcm,bcm5301x-rng", .data = &nsp_rng_of_data },
137 	{ .compatible = "brcm,bcm6368-rng"},
138 	{},
139 };
140 
141 static int bcm2835_rng_probe(struct platform_device *pdev)
142 {
143 	const struct bcm2835_rng_of_data *of_data;
144 	struct device *dev = &pdev->dev;
145 	const struct of_device_id *rng_id;
146 	struct bcm2835_rng_priv *priv;
147 	int err;
148 
149 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
150 	if (!priv)
151 		return -ENOMEM;
152 
153 	platform_set_drvdata(pdev, priv);
154 
155 	/* map peripheral */
156 	priv->base = devm_platform_ioremap_resource(pdev, 0);
157 	if (IS_ERR(priv->base))
158 		return PTR_ERR(priv->base);
159 
160 	/* Clock is optional on most platforms */
161 	priv->clk = devm_clk_get_optional(dev, NULL);
162 	if (IS_ERR(priv->clk))
163 		return PTR_ERR(priv->clk);
164 
165 	priv->reset = devm_reset_control_get_optional_exclusive(dev, NULL);
166 	if (IS_ERR(priv->reset))
167 		return PTR_ERR(priv->reset);
168 
169 	priv->rng.name = pdev->name;
170 	priv->rng.init = bcm2835_rng_init;
171 	priv->rng.read = bcm2835_rng_read;
172 	priv->rng.cleanup = bcm2835_rng_cleanup;
173 
174 	if (dev_of_node(dev)) {
175 		rng_id = of_match_node(bcm2835_rng_of_match, dev->of_node);
176 		if (!rng_id)
177 			return -EINVAL;
178 
179 		/* Check for rng init function, execute it */
180 		of_data = rng_id->data;
181 		if (of_data)
182 			priv->mask_interrupts = of_data->mask_interrupts;
183 	}
184 
185 	/* register driver */
186 	err = devm_hwrng_register(dev, &priv->rng);
187 	if (err)
188 		dev_err(dev, "hwrng registration failed\n");
189 	else
190 		dev_info(dev, "hwrng registered\n");
191 
192 	return err;
193 }
194 
195 MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
196 
197 static const struct platform_device_id bcm2835_rng_devtype[] = {
198 	{ .name = "bcm2835-rng" },
199 	{ .name = "bcm63xx-rng" },
200 	{ /* sentinel */ }
201 };
202 MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
203 
204 static struct platform_driver bcm2835_rng_driver = {
205 	.driver = {
206 		.name = "bcm2835-rng",
207 		.of_match_table = bcm2835_rng_of_match,
208 	},
209 	.probe		= bcm2835_rng_probe,
210 	.id_table	= bcm2835_rng_devtype,
211 };
212 module_platform_driver(bcm2835_rng_driver);
213 
214 MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
215 MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
216 MODULE_LICENSE("GPL v2");
217