1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Nomadik RNG support
4 *  Copyright 2009 Alessandro Rubini
5 */
6
7#include <linux/kernel.h>
8#include <linux/module.h>
9#include <linux/device.h>
10#include <linux/amba/bus.h>
11#include <linux/hw_random.h>
12#include <linux/io.h>
13#include <linux/clk.h>
14#include <linux/err.h>
15
16static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
17{
18	void __iomem *base = (void __iomem *)rng->priv;
19
20	/*
21	 * The register is 32 bits and gives 16 random bits (low half).
22	 * A subsequent read will delay the core for 400ns, so we just read
23	 * once and accept the very unlikely very small delay, even if wait==0.
24	 */
25	*(u16 *)data = __raw_readl(base + 8) & 0xffff;
26	return 2;
27}
28
29/* we have at most one RNG per machine, granted */
30static struct hwrng nmk_rng = {
31	.name		= "nomadik",
32	.read		= nmk_rng_read,
33};
34
35static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
36{
37	struct clk *rng_clk;
38	void __iomem *base;
39	int ret;
40
41	rng_clk = devm_clk_get_enabled(&dev->dev, NULL);
42	if (IS_ERR(rng_clk)) {
43		dev_err(&dev->dev, "could not get rng clock\n");
44		ret = PTR_ERR(rng_clk);
45		return ret;
46	}
47
48	ret = amba_request_regions(dev, dev->dev.init_name);
49	if (ret)
50		return ret;
51	ret = -ENOMEM;
52	base = devm_ioremap(&dev->dev, dev->res.start,
53			    resource_size(&dev->res));
54	if (!base)
55		goto out_release;
56	nmk_rng.priv = (unsigned long)base;
57	ret = devm_hwrng_register(&dev->dev, &nmk_rng);
58	if (ret)
59		goto out_release;
60	return 0;
61
62out_release:
63	amba_release_regions(dev);
64	return ret;
65}
66
67static void nmk_rng_remove(struct amba_device *dev)
68{
69	amba_release_regions(dev);
70}
71
72static const struct amba_id nmk_rng_ids[] = {
73	{
74		.id	= 0x000805e1,
75		.mask	= 0x000fffff, /* top bits are rev and cfg: accept all */
76	},
77	{0, 0},
78};
79
80MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
81
82static struct amba_driver nmk_rng_driver = {
83	.drv = {
84		.owner = THIS_MODULE,
85		.name = "rng",
86		},
87	.probe = nmk_rng_probe,
88	.remove = nmk_rng_remove,
89	.id_table = nmk_rng_ids,
90};
91
92module_amba_driver(nmk_rng_driver);
93
94MODULE_LICENSE("GPL");
95