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
30struct bcm2835_rng_priv {
31	struct hwrng rng;
32	void __iomem *base;
33	bool mask_interrupts;
34	struct clk *clk;
35};
36
37static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
38{
39	return container_of(rng, struct bcm2835_rng_priv, rng);
40}
41
42static 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
53static 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
62static 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
85static 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
111static 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
122struct bcm2835_rng_of_data {
123	bool mask_interrupts;
124};
125
126static const struct bcm2835_rng_of_data nsp_rng_of_data = {
127	.mask_interrupts = true,
128};
129
130static 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
138static 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	const struct of_device_id *rng_id;
143	struct bcm2835_rng_priv *priv;
144	int err;
145
146	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
147	if (!priv)
148		return -ENOMEM;
149
150	platform_set_drvdata(pdev, priv);
151
152	/* map peripheral */
153	priv->base = devm_platform_ioremap_resource(pdev, 0);
154	if (IS_ERR(priv->base))
155		return PTR_ERR(priv->base);
156
157	/* Clock is optional on most platforms */
158	priv->clk = devm_clk_get(dev, NULL);
159	if (PTR_ERR(priv->clk) == -EPROBE_DEFER)
160		return -EPROBE_DEFER;
161
162	priv->rng.name = pdev->name;
163	priv->rng.init = bcm2835_rng_init;
164	priv->rng.read = bcm2835_rng_read;
165	priv->rng.cleanup = bcm2835_rng_cleanup;
166
167	if (dev_of_node(dev)) {
168		rng_id = of_match_node(bcm2835_rng_of_match, dev->of_node);
169		if (!rng_id)
170			return -EINVAL;
171
172		/* Check for rng init function, execute it */
173		of_data = rng_id->data;
174		if (of_data)
175			priv->mask_interrupts = of_data->mask_interrupts;
176	}
177
178	/* register driver */
179	err = devm_hwrng_register(dev, &priv->rng);
180	if (err)
181		dev_err(dev, "hwrng registration failed\n");
182	else
183		dev_info(dev, "hwrng registered\n");
184
185	return err;
186}
187
188MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
189
190static const struct platform_device_id bcm2835_rng_devtype[] = {
191	{ .name = "bcm2835-rng" },
192	{ .name = "bcm63xx-rng" },
193	{ /* sentinel */ }
194};
195MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
196
197static struct platform_driver bcm2835_rng_driver = {
198	.driver = {
199		.name = "bcm2835-rng",
200		.of_match_table = bcm2835_rng_of_match,
201	},
202	.probe		= bcm2835_rng_probe,
203	.id_table	= bcm2835_rng_devtype,
204};
205module_platform_driver(bcm2835_rng_driver);
206
207MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
208MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
209MODULE_LICENSE("GPL v2");
210