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/* $OpenBSD: bcm2835_rng.c,v 1.3 2020/05/29 04:42:25 deraadt Exp $ */
/*
* Copyright (c) 2018 Mark Kettenis <kettenis@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>
#include <sys/timeout.h>
#include <machine/bus.h>
#include <machine/fdt.h>
#include <dev/ofw/openfirm.h>
#include <dev/ofw/fdt.h>
/* Registers */
#define RNG_CTRL 0x0000
#define RNG_CTRL_EN (1 << 0)
#define RNG_STATUS 0x0004
#define RNG_STATUS_COUNT(x) ((x) >> 24)
#define RNG_DATA 0x0008
#define HREAD4(sc, reg) \
(bus_space_read_4((sc)->sc_iot, (sc)->sc_ioh, (reg)))
#define HWRITE4(sc, reg, val) \
bus_space_write_4((sc)->sc_iot, (sc)->sc_ioh, (reg), (val))
struct bcmrng_softc {
struct device sc_dev;
bus_space_tag_t sc_iot;
bus_space_handle_t sc_ioh;
struct timeout sc_to;
};
int bcmrng_match(struct device *, void *, void *);
void bcmrng_attach(struct device *, struct device *, void *);
struct cfattach bcmrng_ca = {
sizeof (struct bcmrng_softc), bcmrng_match, bcmrng_attach
};
struct cfdriver bcmrng_cd = {
NULL, "bcmrng", DV_DULL
};
void bcmrng_rnd(void *);
int
bcmrng_match(struct device *parent, void *match, void *aux)
{
struct fdt_attach_args *faa = aux;
return OF_is_compatible(faa->fa_node, "brcm,bcm2835-rng");
}
void
bcmrng_attach(struct device *parent, struct device *self, void *aux)
{
struct bcmrng_softc *sc = (struct bcmrng_softc *)self;
struct fdt_attach_args *faa = aux;
if (faa->fa_nreg < 1) {
printf(": no registers\n");
return;
}
sc->sc_iot = faa->fa_iot;
if (bus_space_map(sc->sc_iot, faa->fa_reg[0].addr,
faa->fa_reg[0].size, 0, &sc->sc_ioh)) {
printf(": can't map registers\n");
return;
}
printf("\n");
/* Discard initial numbers which may be "less" random. */
HWRITE4(sc, RNG_STATUS, 250000);
HWRITE4(sc, RNG_CTRL, RNG_CTRL_EN);
timeout_set(&sc->sc_to, bcmrng_rnd, sc);
bcmrng_rnd(sc);
}
void
bcmrng_rnd(void *arg)
{
struct bcmrng_softc *sc = arg;
uint32_t status, data;
int i, count;
status = HREAD4(sc, RNG_STATUS);
count = MIN(4, RNG_STATUS_COUNT(status));
for (i = 0; i < count; i++) {
data = HREAD4(sc, RNG_DATA);
enqueue_randomness(data);
}
timeout_add_sec(&sc->sc_to, 1);
}
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