1/*
2 * Nomadik RNG support
3 *  Copyright 2009 Alessandro Rubini
4 *
5 *  This program is free software; you can redistribute it and/or modify
6 *  it under the terms of the GNU General Public License as published by
7 *  the Free Software Foundation; either version 2 of the License, or
8 *  (at your option) any later version.
9 */
10
11#include <linux/kernel.h>
12#include <linux/module.h>
13#include <linux/device.h>
14#include <linux/amba/bus.h>
15#include <linux/hw_random.h>
16#include <linux/io.h>
17#include <linux/clk.h>
18#include <linux/err.h>
19
20static struct clk *rng_clk;
21
22static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
23{
24	void __iomem *base = (void __iomem *)rng->priv;
25
26	/*
27	 * The register is 32 bits and gives 16 random bits (low half).
28	 * A subsequent read will delay the core for 400ns, so we just read
29	 * once and accept the very unlikely very small delay, even if wait==0.
30	 */
31	*(u16 *)data = __raw_readl(base + 8) & 0xffff;
32	return 2;
33}
34
35/* we have at most one RNG per machine, granted */
36static struct hwrng nmk_rng = {
37	.name		= "nomadik",
38	.read		= nmk_rng_read,
39};
40
41static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
42{
43	void __iomem *base;
44	int ret;
45
46	rng_clk = devm_clk_get(&dev->dev, NULL);
47	if (IS_ERR(rng_clk)) {
48		dev_err(&dev->dev, "could not get rng clock\n");
49		ret = PTR_ERR(rng_clk);
50		return ret;
51	}
52
53	clk_prepare_enable(rng_clk);
54
55	ret = amba_request_regions(dev, dev->dev.init_name);
56	if (ret)
57		goto out_clk;
58	ret = -ENOMEM;
59	base = devm_ioremap(&dev->dev, dev->res.start,
60			    resource_size(&dev->res));
61	if (!base)
62		goto out_release;
63	nmk_rng.priv = (unsigned long)base;
64	ret = hwrng_register(&nmk_rng);
65	if (ret)
66		goto out_release;
67	return 0;
68
69out_release:
70	amba_release_regions(dev);
71out_clk:
72	clk_disable(rng_clk);
73	return ret;
74}
75
76static int nmk_rng_remove(struct amba_device *dev)
77{
78	hwrng_unregister(&nmk_rng);
79	amba_release_regions(dev);
80	clk_disable(rng_clk);
81	return 0;
82}
83
84static struct amba_id nmk_rng_ids[] = {
85	{
86		.id	= 0x000805e1,
87		.mask	= 0x000fffff, /* top bits are rev and cfg: accept all */
88	},
89	{0, 0},
90};
91
92MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
93
94static struct amba_driver nmk_rng_driver = {
95	.drv = {
96		.owner = THIS_MODULE,
97		.name = "rng",
98		},
99	.probe = nmk_rng_probe,
100	.remove = nmk_rng_remove,
101	.id_table = nmk_rng_ids,
102};
103
104module_amba_driver(nmk_rng_driver);
105
106MODULE_LICENSE("GPL");
107