1 /* $NetBSD: bcm2835_rng.c,v 1.17 2022/03/19 11:55:03 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2013 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jared D. McNeill
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 __KERNEL_RCSID(0, "$NetBSD: bcm2835_rng.c,v 1.17 2022/03/19 11:55:03 riastradh Exp $");
34
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/device.h>
38 #include <sys/kernel.h>
39 #include <sys/bus.h>
40 #include <sys/rndsource.h>
41
42 #include <arm/broadcom/bcm2835reg.h>
43 #include <arm/broadcom/bcm2835_intr.h>
44
45 #include <dev/fdt/fdtvar.h>
46
47 #define RNG_CTRL 0x00
48 #define RNG_CTRL_EN __BIT(0)
49 #define RNG_STATUS 0x04
50 #define RNG_STATUS_CNT __BITS(31,24)
51 #define RNG_DATA 0x08
52
53 #define RNG_DATA_MAX 256
54
55 struct bcm2835rng_softc {
56 device_t sc_dev;
57
58 bus_space_tag_t sc_iot;
59 bus_space_handle_t sc_ioh;
60
61 krndsource_t sc_rndsource;
62 };
63
64 static int bcmrng_match(device_t, cfdata_t, void *);
65 static void bcmrng_attach(device_t, device_t, void *);
66 static void bcmrng_get(size_t, void *);
67
68 CFATTACH_DECL_NEW(bcmrng_fdt, sizeof(struct bcm2835rng_softc),
69 bcmrng_match, bcmrng_attach, NULL, NULL);
70
71 static const struct device_compatible_entry compat_data[] = {
72 { .compat = "brcm,bcm2835-rng" },
73 DEVICE_COMPAT_EOL
74 };
75
76 /* ARGSUSED */
77 static int
bcmrng_match(device_t parent,cfdata_t match,void * aux)78 bcmrng_match(device_t parent, cfdata_t match, void *aux)
79 {
80 struct fdt_attach_args * const faa = aux;
81
82 return of_compatible_match(faa->faa_phandle, compat_data);
83 }
84
85 static void
bcmrng_attach(device_t parent,device_t self,void * aux)86 bcmrng_attach(device_t parent, device_t self, void *aux)
87 {
88 struct bcm2835rng_softc *sc = device_private(self);
89 struct fdt_attach_args * const faa = aux;
90 const int phandle = faa->faa_phandle;
91 uint32_t ctrl;
92 bus_addr_t addr;
93 bus_size_t size;
94 int error;
95
96 aprint_naive("\n");
97 aprint_normal(": RNG\n");
98
99 sc->sc_dev = self;
100 sc->sc_iot = faa->faa_bst;
101
102 error = fdtbus_get_reg(phandle, 0, &addr, &size);
103 if (error) {
104 aprint_error_dev(sc->sc_dev, "unable to map device\n");
105 return;
106 }
107
108 if (bus_space_map(sc->sc_iot, addr, size, 0,
109 &sc->sc_ioh)) {
110 aprint_error_dev(sc->sc_dev, "unable to map device\n");
111 return;
112 }
113
114 /* discard initial numbers, broadcom says they are "less random" */
115 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000);
116
117 /* enable rng */
118 ctrl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL);
119 ctrl |= RNG_CTRL_EN;
120 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl);
121
122 /* set up an rndsource */
123 rndsource_setcb(&sc->sc_rndsource, &bcmrng_get, sc);
124 rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG,
125 RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
126 }
127
128 static void
bcmrng_get(size_t bytes_wanted,void * arg)129 bcmrng_get(size_t bytes_wanted, void *arg)
130 {
131 struct bcm2835rng_softc *sc = arg;
132 uint32_t status, cnt;
133 uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */
134
135 while (bytes_wanted) {
136 status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS);
137 cnt = __SHIFTOUT(status, RNG_STATUS_CNT);
138 KASSERT(cnt < RNG_DATA_MAX);
139 if (cnt == 0)
140 continue; /* XXX Busy-waiting seems wrong... */
141 bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf,
142 cnt);
143 rnd_add_data_sync(&sc->sc_rndsource, buf, (cnt * 4),
144 (cnt * 4 * NBBY));
145 bytes_wanted -= MIN(bytes_wanted, (cnt * 4));
146 }
147 explicit_memset(buf, 0, sizeof(buf));
148 }
149