bcm2835_rng.c revision 1.11
1/* $NetBSD: bcm2835_rng.c,v 1.11 2015/04/13 21:18:40 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 1.11 2015/04/13 21:18:40 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/rndpool.h> 41#include <sys/rndsource.h> 42#include <sys/atomic.h> 43#include <sys/intr.h> 44 45#include <arm/broadcom/bcm_amba.h> 46#include <arm/broadcom/bcm2835reg.h> 47#include <arm/broadcom/bcm2835_intr.h> 48 49#define RNG_CTRL 0x00 50#define RNG_CTRL_EN __BIT(0) 51#define RNG_STATUS 0x04 52#define RNG_STATUS_CNT __BITS(31,24) 53#define RNG_DATA 0x08 54 55#define RNG_DATA_MAX 256 56 57struct bcm2835rng_softc { 58 device_t sc_dev; 59 60 bus_space_tag_t sc_iot; 61 bus_space_handle_t sc_ioh; 62 63 kmutex_t sc_intr_lock; 64 unsigned int sc_bytes_wanted; 65 void *sc_sih; 66 67 kmutex_t sc_rnd_lock; 68 krndsource_t sc_rndsource; 69}; 70 71static int bcmrng_match(device_t, cfdata_t, void *); 72static void bcmrng_attach(device_t, device_t, void *); 73static void bcmrng_get(struct bcm2835rng_softc *); 74static void bcmrng_get_cb(size_t, void *); 75static void bcmrng_get_intr(void *); 76 77CFATTACH_DECL_NEW(bcmrng_amba, sizeof(struct bcm2835rng_softc), 78 bcmrng_match, bcmrng_attach, NULL, NULL); 79 80/* ARGSUSED */ 81static int 82bcmrng_match(device_t parent, cfdata_t match, void *aux) 83{ 84 struct amba_attach_args *aaa = aux; 85 86 if (strcmp(aaa->aaa_name, "bcmrng") != 0) 87 return 0; 88 89 return 1; 90} 91 92static void 93bcmrng_attach(device_t parent, device_t self, void *aux) 94{ 95 struct bcm2835rng_softc *sc = device_private(self); 96 struct amba_attach_args *aaa = aux; 97 uint32_t ctrl; 98 99 aprint_naive("\n"); 100 aprint_normal(": RNG\n"); 101 102 sc->sc_dev = self; 103 sc->sc_iot = aaa->aaa_iot; 104 105 if (bus_space_map(aaa->aaa_iot, aaa->aaa_addr, BCM2835_RNG_SIZE, 0, 106 &sc->sc_ioh)) { 107 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 108 goto fail0; 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 a softint for adding data */ 120 mutex_init(&sc->sc_intr_lock, MUTEX_DEFAULT, IPL_SERIAL); 121 sc->sc_bytes_wanted = 0; 122 sc->sc_sih = softint_establish(SOFTINT_SERIAL|SOFTINT_MPSAFE, 123 &bcmrng_get_intr, sc); 124 if (sc->sc_sih == NULL) { 125 aprint_error_dev(sc->sc_dev, "unable to establish softint"); 126 goto fail1; 127 } 128 129 /* set up an rndsource */ 130 mutex_init(&sc->sc_rnd_lock, MUTEX_DEFAULT, IPL_SERIAL); 131 rndsource_setcb(&sc->sc_rndsource, &bcmrng_get_cb, sc); 132 rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG, 133 RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB); 134 135 /* get some initial entropy ASAP */ 136 bcmrng_get_cb(RND_POOLBITS / NBBY, sc); 137 138 /* Success! */ 139 return; 140 141fail1: mutex_destroy(&sc->sc_intr_lock); 142 bus_space_unmap(aaa->aaa_iot, sc->sc_ioh, BCM2835_RNG_SIZE); 143fail0: return; 144} 145 146static void 147bcmrng_get(struct bcm2835rng_softc *sc) 148{ 149 uint32_t status, cnt; 150 uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */ 151 152 mutex_spin_enter(&sc->sc_intr_lock); 153 while (sc->sc_bytes_wanted) { 154 status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS); 155 cnt = __SHIFTOUT(status, RNG_STATUS_CNT); 156 KASSERT(cnt < RNG_DATA_MAX); 157 if (cnt == 0) 158 continue; /* XXX Busy-waiting seems wrong... */ 159 bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf, 160 cnt); 161 162 /* 163 * This lock dance is necessary because rnd_add_data 164 * may call bcmrng_get_cb which takes the intr lock. 165 */ 166 mutex_spin_exit(&sc->sc_intr_lock); 167 mutex_spin_enter(&sc->sc_rnd_lock); 168 rnd_add_data(&sc->sc_rndsource, buf, (cnt * 4), 169 (cnt * 4 * NBBY)); 170 mutex_spin_exit(&sc->sc_rnd_lock); 171 mutex_spin_enter(&sc->sc_intr_lock); 172 sc->sc_bytes_wanted -= MIN(sc->sc_bytes_wanted, (cnt * 4)); 173 } 174 explicit_memset(buf, 0, sizeof(buf)); 175 mutex_spin_exit(&sc->sc_intr_lock); 176} 177 178static void 179bcmrng_get_cb(size_t bytes_wanted, void *arg) 180{ 181 struct bcm2835rng_softc *sc = arg; 182 183 /* 184 * Deferring to a softint is necessary until the rnd(9) locking 185 * is fixed. 186 */ 187 mutex_spin_enter(&sc->sc_intr_lock); 188 if (sc->sc_bytes_wanted == 0) 189 softint_schedule(sc->sc_sih); 190 if (bytes_wanted > (UINT_MAX - sc->sc_bytes_wanted)) 191 sc->sc_bytes_wanted = UINT_MAX; 192 else 193 sc->sc_bytes_wanted += bytes_wanted; 194 mutex_spin_exit(&sc->sc_intr_lock); 195} 196 197static void 198bcmrng_get_intr(void *arg) 199{ 200 struct bcm2835rng_softc *const sc = arg; 201 202 bcmrng_get(sc); 203} 204