1 /* $OpenBSD: bcm2835_rng.c,v 1.4 2021/10/24 17:52:26 mpi Exp $ */
2 /*
3 * Copyright (c) 2018 Mark Kettenis <kettenis@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <sys/param.h>
19 #include <sys/systm.h>
20 #include <sys/device.h>
21 #include <sys/timeout.h>
22
23 #include <machine/bus.h>
24 #include <machine/fdt.h>
25
26 #include <dev/ofw/openfirm.h>
27 #include <dev/ofw/fdt.h>
28
29 /* Registers */
30 #define RNG_CTRL 0x0000
31 #define RNG_CTRL_EN (1 << 0)
32 #define RNG_STATUS 0x0004
33 #define RNG_STATUS_COUNT(x) ((x) >> 24)
34 #define RNG_DATA 0x0008
35
36 #define HREAD4(sc, reg) \
37 (bus_space_read_4((sc)->sc_iot, (sc)->sc_ioh, (reg)))
38 #define HWRITE4(sc, reg, val) \
39 bus_space_write_4((sc)->sc_iot, (sc)->sc_ioh, (reg), (val))
40
41 struct bcmrng_softc {
42 struct device sc_dev;
43 bus_space_tag_t sc_iot;
44 bus_space_handle_t sc_ioh;
45
46 struct timeout sc_to;
47 };
48
49 int bcmrng_match(struct device *, void *, void *);
50 void bcmrng_attach(struct device *, struct device *, void *);
51
52 const struct cfattach bcmrng_ca = {
53 sizeof (struct bcmrng_softc), bcmrng_match, bcmrng_attach
54 };
55
56 struct cfdriver bcmrng_cd = {
57 NULL, "bcmrng", DV_DULL
58 };
59
60 void bcmrng_rnd(void *);
61
62 int
bcmrng_match(struct device * parent,void * match,void * aux)63 bcmrng_match(struct device *parent, void *match, void *aux)
64 {
65 struct fdt_attach_args *faa = aux;
66
67 return OF_is_compatible(faa->fa_node, "brcm,bcm2835-rng");
68 }
69
70 void
bcmrng_attach(struct device * parent,struct device * self,void * aux)71 bcmrng_attach(struct device *parent, struct device *self, void *aux)
72 {
73 struct bcmrng_softc *sc = (struct bcmrng_softc *)self;
74 struct fdt_attach_args *faa = aux;
75
76 if (faa->fa_nreg < 1) {
77 printf(": no registers\n");
78 return;
79 }
80
81 sc->sc_iot = faa->fa_iot;
82 if (bus_space_map(sc->sc_iot, faa->fa_reg[0].addr,
83 faa->fa_reg[0].size, 0, &sc->sc_ioh)) {
84 printf(": can't map registers\n");
85 return;
86 }
87
88 printf("\n");
89
90 /* Discard initial numbers which may be "less" random. */
91 HWRITE4(sc, RNG_STATUS, 250000);
92 HWRITE4(sc, RNG_CTRL, RNG_CTRL_EN);
93
94 timeout_set(&sc->sc_to, bcmrng_rnd, sc);
95 bcmrng_rnd(sc);
96 }
97
98 void
bcmrng_rnd(void * arg)99 bcmrng_rnd(void *arg)
100 {
101 struct bcmrng_softc *sc = arg;
102 uint32_t status, data;
103 int i, count;
104
105 status = HREAD4(sc, RNG_STATUS);
106 count = MIN(4, RNG_STATUS_COUNT(status));
107 for (i = 0; i < count; i++) {
108 data = HREAD4(sc, RNG_DATA);
109 enqueue_randomness(data);
110 }
111
112 timeout_add_sec(&sc->sc_to, 1);
113 }
114