1 /* $NetBSD: bcm2835_rng.c,v 1.13 2017/12/10 21:38:26 skrll 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 1.13 2017/12/10 21:38:26 skrll 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 43 #include <arm/broadcom/bcm2835reg.h> 44 #include <arm/broadcom/bcm2835_intr.h> 45 46 #include <dev/fdt/fdtvar.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_lock; 63 krndsource_t sc_rndsource; 64 }; 65 66 static int bcmrng_match(device_t, cfdata_t, void *); 67 static void bcmrng_attach(device_t, device_t, void *); 68 static void bcmrng_get(size_t, void *); 69 70 CFATTACH_DECL_NEW(bcmrng_fdt, sizeof(struct bcm2835rng_softc), 71 bcmrng_match, bcmrng_attach, NULL, NULL); 72 73 /* ARGSUSED */ 74 static int 75 bcmrng_match(device_t parent, cfdata_t match, void *aux) 76 { 77 const char * const compatible[] = { "brcm,bcm2835-rng", NULL }; 78 struct fdt_attach_args * const faa = aux; 79 80 return of_match_compatible(faa->faa_phandle, compatible); 81 } 82 83 static void 84 bcmrng_attach(device_t parent, device_t self, void *aux) 85 { 86 struct bcm2835rng_softc *sc = device_private(self); 87 struct fdt_attach_args * const faa = aux; 88 const int phandle = faa->faa_phandle; 89 uint32_t ctrl; 90 bus_addr_t addr; 91 bus_size_t size; 92 int error; 93 94 aprint_naive("\n"); 95 aprint_normal(": RNG\n"); 96 97 sc->sc_dev = self; 98 sc->sc_iot = faa->faa_bst; 99 100 error = fdtbus_get_reg(phandle, 0, &addr, &size); 101 if (error) { 102 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 103 return; 104 } 105 106 if (bus_space_map(sc->sc_iot, addr, size, 0, 107 &sc->sc_ioh)) { 108 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 109 return; 110 } 111 112 /* discard initial numbers, broadcom says they are "less random" */ 113 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000); 114 115 /* enable rng */ 116 ctrl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL); 117 ctrl |= RNG_CTRL_EN; 118 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl); 119 120 /* set up an rndsource */ 121 mutex_init(&sc->sc_lock, MUTEX_DEFAULT, IPL_VM); 122 rndsource_setcb(&sc->sc_rndsource, &bcmrng_get, sc); 123 rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG, 124 RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB); 125 126 /* get some initial entropy ASAP */ 127 bcmrng_get(RND_POOLBITS / NBBY, sc); 128 } 129 130 static void 131 bcmrng_get(size_t bytes_wanted, void *arg) 132 { 133 struct bcm2835rng_softc *sc = arg; 134 uint32_t status, cnt; 135 uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */ 136 137 mutex_spin_enter(&sc->sc_lock); 138 while (bytes_wanted) { 139 status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS); 140 cnt = __SHIFTOUT(status, RNG_STATUS_CNT); 141 KASSERT(cnt < RNG_DATA_MAX); 142 if (cnt == 0) 143 continue; /* XXX Busy-waiting seems wrong... */ 144 bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf, 145 cnt); 146 rnd_add_data_sync(&sc->sc_rndsource, buf, (cnt * 4), 147 (cnt * 4 * NBBY)); 148 bytes_wanted -= MIN(bytes_wanted, (cnt * 4)); 149 } 150 explicit_memset(buf, 0, sizeof(buf)); 151 mutex_spin_exit(&sc->sc_lock); 152 } 153