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");