bcm2835_rng.c revision 1.10
1/* $NetBSD: bcm2835_rng.c,v 1.10 2014/08/10 16:44:33 tls 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 1.10 2014/08/10 16:44:33 tls 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/rnd.h> 41#include <sys/atomic.h> 42#include <sys/intr.h> 43 44#include <arm/broadcom/bcm_amba.h> 45#include <arm/broadcom/bcm2835reg.h> 46#include <arm/broadcom/bcm2835_intr.h> 47 48#define RNG_CTRL 0x00 49#define RNG_CTRL_EN __BIT(0) 50#define RNG_STATUS 0x04 51#define RNG_STATUS_CNT __BITS(31,24) 52#define RNG_DATA 0x08 53 54#define RNG_DATA_MAX 256 55 56struct bcm2835rng_softc { 57 device_t sc_dev; 58 59 bus_space_tag_t sc_iot; 60 bus_space_handle_t sc_ioh; 61 62 kmutex_t sc_intr_lock; 63 unsigned int sc_bytes_wanted; 64 void *sc_sih; 65 66 kmutex_t sc_rnd_lock; 67 krndsource_t sc_rndsource; 68}; 69 70static int bcmrng_match(device_t, cfdata_t, void *); 71static void bcmrng_attach(device_t, device_t, void *); 72static void bcmrng_get(struct bcm2835rng_softc *); 73static void bcmrng_get_cb(size_t, void *); 74static void bcmrng_get_intr(void *); 75 76CFATTACH_DECL_NEW(bcmrng_amba, sizeof(struct bcm2835rng_softc), 77 bcmrng_match, bcmrng_attach, NULL, NULL); 78 79/* ARGSUSED */ 80static int 81bcmrng_match(device_t parent, cfdata_t match, void *aux) 82{ 83 struct amba_attach_args *aaa = aux; 84 85 if (strcmp(aaa->aaa_name, "bcmrng") != 0) 86 return 0; 87 88 return 1; 89} 90 91static void 92bcmrng_attach(device_t parent, device_t self, void *aux) 93{ 94 struct bcm2835rng_softc *sc = device_private(self); 95 struct amba_attach_args *aaa = aux; 96 uint32_t ctrl; 97 98 aprint_naive("\n"); 99 aprint_normal(": RNG\n"); 100 101 sc->sc_dev = self; 102 sc->sc_iot = aaa->aaa_iot; 103 104 if (bus_space_map(aaa->aaa_iot, aaa->aaa_addr, BCM2835_RNG_SIZE, 0, 105 &sc->sc_ioh)) { 106 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 107 goto fail0; 108 } 109 110 /* discard initial numbers, broadcom says they are "less random" */ 111 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000); 112 113 /* enable rng */ 114 ctrl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL); 115 ctrl |= RNG_CTRL_EN; 116 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl); 117 118 /* set up a softint for adding data */ 119 mutex_init(&sc->sc_intr_lock, MUTEX_DEFAULT, IPL_SERIAL); 120 sc->sc_bytes_wanted = 0; 121 sc->sc_sih = softint_establish(SOFTINT_SERIAL|SOFTINT_MPSAFE, 122 &bcmrng_get_intr, sc); 123 if (sc->sc_sih == NULL) { 124 aprint_error_dev(sc->sc_dev, "unable to establish softint"); 125 goto fail1; 126 } 127 128 /* set up an rndsource */ 129 mutex_init(&sc->sc_rnd_lock, MUTEX_DEFAULT, IPL_SERIAL); 130 rndsource_setcb(&sc->sc_rndsource, &bcmrng_get_cb, sc); 131 rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG, 132 RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB); 133 134 /* get some initial entropy ASAP */ 135 bcmrng_get_cb(RND_POOLBITS / NBBY, sc); 136 137 /* Success! */ 138 return; 139 140fail1: mutex_destroy(&sc->sc_intr_lock); 141 bus_space_unmap(aaa->aaa_iot, sc->sc_ioh, BCM2835_RNG_SIZE); 142fail0: return; 143} 144 145static void 146bcmrng_get(struct bcm2835rng_softc *sc) 147{ 148 uint32_t status, cnt; 149 uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */ 150 151 mutex_spin_enter(&sc->sc_intr_lock); 152 while (sc->sc_bytes_wanted) { 153 status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS); 154 cnt = __SHIFTOUT(status, RNG_STATUS_CNT); 155 KASSERT(cnt < RNG_DATA_MAX); 156 if (cnt == 0) 157 continue; /* XXX Busy-waiting seems wrong... */ 158 bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf, 159 cnt); 160 161 /* 162 * This lock dance is necessary because rnd_add_data 163 * may call bcmrng_get_cb which takes the intr lock. 164 */ 165 mutex_spin_exit(&sc->sc_intr_lock); 166 mutex_spin_enter(&sc->sc_rnd_lock); 167 rnd_add_data(&sc->sc_rndsource, buf, (cnt * 4), 168 (cnt * 4 * NBBY)); 169 mutex_spin_exit(&sc->sc_rnd_lock); 170 mutex_spin_enter(&sc->sc_intr_lock); 171 sc->sc_bytes_wanted -= MIN(sc->sc_bytes_wanted, (cnt * 4)); 172 } 173 explicit_memset(buf, 0, sizeof(buf)); 174 mutex_spin_exit(&sc->sc_intr_lock); 175} 176 177static void 178bcmrng_get_cb(size_t bytes_wanted, void *arg) 179{ 180 struct bcm2835rng_softc *sc = arg; 181 182 /* 183 * Deferring to a softint is necessary until the rnd(9) locking 184 * is fixed. 185 */ 186 mutex_spin_enter(&sc->sc_intr_lock); 187 if (sc->sc_bytes_wanted == 0) 188 softint_schedule(sc->sc_sih); 189 if (bytes_wanted > (UINT_MAX - sc->sc_bytes_wanted)) 190 sc->sc_bytes_wanted = UINT_MAX; 191 else 192 sc->sc_bytes_wanted += bytes_wanted; 193 mutex_spin_exit(&sc->sc_intr_lock); 194} 195 196static void 197bcmrng_get_intr(void *arg) 198{ 199 struct bcm2835rng_softc *const sc = arg; 200 201 bcmrng_get(sc); 202} 203