bcm2835_rng.c revision 1.14 
1/*	$NetBSD: bcm2835_rng.c,v 1.14 2020/04/30 03:40:52 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 1.14 2020/04/30 03:40:52 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
55struct bcm2835rng_softc {
56	device_t		sc_dev;
57
58	bus_space_tag_t		sc_iot;
59	bus_space_handle_t	sc_ioh;
60
61	kmutex_t		sc_lock;
62	krndsource_t		sc_rndsource;
63};
64
65static int bcmrng_match(device_t, cfdata_t, void *);
66static void bcmrng_attach(device_t, device_t, void *);
67static void bcmrng_get(size_t, void *);
68
69CFATTACH_DECL_NEW(bcmrng_fdt, sizeof(struct bcm2835rng_softc),
70    bcmrng_match, bcmrng_attach, NULL, NULL);
71
72/* ARGSUSED */
73static int
74bcmrng_match(device_t parent, cfdata_t match, void *aux)
75{
76	const char * const compatible[] = { "brcm,bcm2835-rng", NULL };
77	struct fdt_attach_args * const faa = aux;
78
79	return of_match_compatible(faa->faa_phandle, compatible);
80}
81
82static void
83bcmrng_attach(device_t parent, device_t self, void *aux)
84{
85	struct bcm2835rng_softc *sc = device_private(self);
86	struct fdt_attach_args * const faa = aux;
87	const int phandle = faa->faa_phandle;
88	uint32_t ctrl;
89	bus_addr_t addr;
90	bus_size_t size;
91	int error;
92
93	aprint_naive("\n");
94	aprint_normal(": RNG\n");
95
96	sc->sc_dev = self;
97	sc->sc_iot = faa->faa_bst;
98
99	error = fdtbus_get_reg(phandle, 0, &addr, &size);
100	if (error) {
101		aprint_error_dev(sc->sc_dev, "unable to map device\n");
102		return;
103	}
104
105	if (bus_space_map(sc->sc_iot, addr, size, 0,
106	    &sc->sc_ioh)) {
107		aprint_error_dev(sc->sc_dev, "unable to map device\n");
108		return;
109	}
110
111	/* discard initial numbers, broadcom says they are "less random" */
112	bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000);
113
114	/* enable rng */
115	ctrl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL);
116	ctrl |= RNG_CTRL_EN;
117	bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl);
118
119	/* set up an rndsource */
120	mutex_init(&sc->sc_lock, MUTEX_DEFAULT, IPL_VM);
121	rndsource_setcb(&sc->sc_rndsource, &bcmrng_get, sc);
122	rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG,
123	    RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
124}
125
126static void
127bcmrng_get(size_t bytes_wanted, void *arg)
128{
129	struct bcm2835rng_softc *sc = arg;
130	uint32_t status, cnt;
131	uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */
132
133	mutex_spin_enter(&sc->sc_lock);
134	while (bytes_wanted) {
135		status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS);
136		cnt = __SHIFTOUT(status, RNG_STATUS_CNT);
137		KASSERT(cnt < RNG_DATA_MAX);
138		if (cnt == 0)
139			continue;	/* XXX Busy-waiting seems wrong...  */
140		bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf,
141		    cnt);
142		rnd_add_data_sync(&sc->sc_rndsource, buf, (cnt * 4),
143		    (cnt * 4 * NBBY));
144		bytes_wanted -= MIN(bytes_wanted, (cnt * 4));
145	}
146	explicit_memset(buf, 0, sizeof(buf));
147	mutex_spin_exit(&sc->sc_lock);
148}
149