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/init.h>
14 #include <linux/device.h>
15 #include <linux/amba/bus.h>
16 #include <linux/hw_random.h>
19 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
21 void __iomem *base = (void __iomem *)rng->priv;
24 * The register is 32 bits and gives 16 random bits (low half).
25 * A subsequent read will delay the core for 400ns, so we just read
26 * once and accept the very unlikely very small delay, even if wait==0.
28 *(u16 *)data = __raw_readl(base + 8) & 0xffff;
32 /* we have at most one RNG per machine, granted */
33 static struct hwrng nmk_rng = {
38 static int nmk_rng_probe(struct amba_device *dev, struct amba_id *id)
43 ret = amba_request_regions(dev, dev->dev.init_name);
47 base = ioremap(dev->res.start, resource_size(&dev->res));
50 nmk_rng.priv = (unsigned long)base;
51 ret = hwrng_register(&nmk_rng);
59 amba_release_regions(dev);
63 static int nmk_rng_remove(struct amba_device *dev)
65 void __iomem *base = (void __iomem *)nmk_rng.priv;
66 hwrng_unregister(&nmk_rng);
68 amba_release_regions(dev);
72 static struct amba_id nmk_rng_ids[] = {
75 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */
80 static struct amba_driver nmk_rng_driver = {
85 .probe = nmk_rng_probe,
86 .remove = nmk_rng_remove,
87 .id_table = nmk_rng_ids,
90 static int __init nmk_rng_init(void)
92 return amba_driver_register(&nmk_rng_driver);
95 static void __devexit nmk_rng_exit(void)
97 amba_driver_unregister(&nmk_rng_driver);
100 module_init(nmk_rng_init);
101 module_exit(nmk_rng_exit);
103 MODULE_LICENSE("GPL");