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	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
192MODULE_DEVICE_TABLE(of, bcm2835_rng_of_match);
193
194static struct platform_device_id bcm2835_rng_devtype[] = {
195	{ .name = "bcm2835-rng" },
196	{ .name = "bcm63xx-rng" },
197	{ /* sentinel */ }
198};
199MODULE_DEVICE_TABLE(platform, bcm2835_rng_devtype);
200
201static 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};
209module_platform_driver(bcm2835_rng_driver);
210
211MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
212MODULE_DESCRIPTION("BCM2835 Random Number Generator (RNG) driver");
213MODULE_LICENSE("GPL v2");