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
30struct 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
38static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
39{
40	return container_of(rng, struct bcm2835_rng_priv, rng);
41}
42
43static 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
54static 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
63static 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_yield(rng);
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
86static 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
114static 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
124struct bcm2835_rng_of_data {
125	bool mask_interrupts;
126};
127
128static const struct bcm2835_rng_of_data nsp_rng_of_data = {
129	.mask_interrupts = true,
130};
131
132static 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
140static 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
194MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
195
196static const struct platform_device_id bcm2835_rng_devtype[] = {
197	{ .name = "bcm2835-rng" },
198	{ .name = "bcm63xx-rng" },
199	{ /* sentinel */ }
200};
201MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
202
203static 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};
211module_platform_driver(bcm2835_rng_driver);
212
213MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
214MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
215MODULE_LICENSE("GPL v2");
216