1 /* $NetBSD: bcm2835_rng.c,v 1.9 2013/08/29 21:54:11 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 1.9 2013/08/29 21:54:11 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/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 56 struct 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 70 static int bcmrng_match(device_t, cfdata_t, void *); 71 static void bcmrng_attach(device_t, device_t, void *); 72 static void bcmrng_get(struct bcm2835rng_softc *); 73 static void bcmrng_get_cb(size_t, void *); 74 static void bcmrng_get_intr(void *); 75 76 CFATTACH_DECL_NEW(bcmrng_amba, sizeof(struct bcm2835rng_softc), 77 bcmrng_match, bcmrng_attach, NULL, NULL); 78 79 /* ARGSUSED */ 80 static int 81 bcmrng_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 91 static void 92 bcmrng_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_NO_ESTIMATE|RND_FLAG_HASCB); 133 134 /* get some initial entropy ASAP */ 135 bcmrng_get_cb(RND_POOLBITS / NBBY, sc); 136 137 /* Success! */ 138 return; 139 140 fail1: mutex_destroy(&sc->sc_intr_lock); 141 bus_space_unmap(aaa->aaa_iot, sc->sc_ioh, BCM2835_RNG_SIZE); 142 fail0: return; 143 } 144 145 static void 146 bcmrng_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 } 176 177 static void 178 bcmrng_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 } 195 196 static void 197 bcmrng_get_intr(void *arg) 198 { 199 struct bcm2835rng_softc *const sc = arg; 200 201 bcmrng_get(sc); 202 } 203