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