3 * Copyright 2009 Alessandro Rubini
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.
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>
17 #include <linux/clk.h>
18 #include <linux/err.h>
20 static struct clk *rng_clk;
22 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
24 void __iomem *base = (void __iomem *)rng->priv;
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.
31 *(u16 *)data = __raw_readl(base + 8) & 0xffff;
35 /* we have at most one RNG per machine, granted */
36 static struct hwrng nmk_rng = {
41 static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
46 rng_clk = 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);
53 clk_prepare_enable(rng_clk);
55 ret = amba_request_regions(dev, dev->dev.init_name);
59 base = ioremap(dev->res.start, resource_size(&dev->res));
62 nmk_rng.priv = (unsigned long)base;
63 ret = hwrng_register(&nmk_rng);
71 amba_release_regions(dev);
78 static int nmk_rng_remove(struct amba_device *dev)
80 void __iomem *base = (void __iomem *)nmk_rng.priv;
81 hwrng_unregister(&nmk_rng);
83 amba_release_regions(dev);
89 static struct amba_id nmk_rng_ids[] = {
92 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */
97 MODULE_DEVICE_TABLE(amba, nmk_rng_ids);
99 static struct amba_driver nmk_rng_driver = {
101 .owner = THIS_MODULE,
104 .probe = nmk_rng_probe,
105 .remove = nmk_rng_remove,
106 .id_table = nmk_rng_ids,
109 module_amba_driver(nmk_rng_driver);
111 MODULE_LICENSE("GPL");