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		return dev_err_probe(&dev->dev, PTR_ERR(rng_clk), "could not get rng clock\n");
44
45	ret = amba_request_regions(dev, dev->dev.init_name);
46	if (ret)
47		return ret;
48	ret = -ENOMEM;
49	base = devm_ioremap(&dev->dev, dev->res.start,
50			    resource_size(&dev->res));
51	if (!base)
52		goto out_release;
53	nmk_rng.priv = (unsigned long)base;
54	ret = devm_hwrng_register(&dev->dev, &nmk_rng);
55	if (ret)
56		goto out_release;
57	return 0;
58
59out_release:
60	amba_release_regions(dev);
61	return ret;
62}
63
64static void nmk_rng_remove(struct amba_device *dev)
65{
66	amba_release_regions(dev);
67}
68
69static const struct amba_id nmk_rng_ids[] = {
70	{
71		.id	= 0x000805e1,
72		.mask	= 0x000fffff, /* top bits are rev and cfg: accept all */
73	},
74	{0, 0},
75};
76
77MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
78
79static struct amba_driver nmk_rng_driver = {
80	.drv = {
81		.owner = THIS_MODULE,
82		.name = "rng",
83		},
84	.probe = nmk_rng_probe,
85	.remove = nmk_rng_remove,
86	.id_table = nmk_rng_ids,
87};
88
89module_amba_driver(nmk_rng_driver);
90
91MODULE_DESCRIPTION("ST-Ericsson Nomadik Random Number Generator");
92MODULE_LICENSE("GPL");