1 /* $NetBSD: bcm2835_rng.c,v 1.17 2022/03/19 11:55:03 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 1.17 2022/03/19 11:55:03 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 55 struct bcm2835rng_softc { 56 device_t sc_dev; 57 58 bus_space_tag_t sc_iot; 59 bus_space_handle_t sc_ioh; 60 61 krndsource_t sc_rndsource; 62 }; 63 64 static int bcmrng_match(device_t, cfdata_t, void *); 65 static void bcmrng_attach(device_t, device_t, void *); 66 static void bcmrng_get(size_t, void *); 67 68 CFATTACH_DECL_NEW(bcmrng_fdt, sizeof(struct bcm2835rng_softc), 69 bcmrng_match, bcmrng_attach, NULL, NULL); 70 71 static const struct device_compatible_entry compat_data[] = { 72 { .compat = "brcm,bcm2835-rng" }, 73 DEVICE_COMPAT_EOL 74 }; 75 76 /* ARGSUSED */ 77 static int 78 bcmrng_match(device_t parent, cfdata_t match, void *aux) 79 { 80 struct fdt_attach_args * const faa = aux; 81 82 return of_compatible_match(faa->faa_phandle, compat_data); 83 } 84 85 static void 86 bcmrng_attach(device_t parent, device_t self, void *aux) 87 { 88 struct bcm2835rng_softc *sc = device_private(self); 89 struct fdt_attach_args * const faa = aux; 90 const int phandle = faa->faa_phandle; 91 uint32_t ctrl; 92 bus_addr_t addr; 93 bus_size_t size; 94 int error; 95 96 aprint_naive("\n"); 97 aprint_normal(": RNG\n"); 98 99 sc->sc_dev = self; 100 sc->sc_iot = faa->faa_bst; 101 102 error = fdtbus_get_reg(phandle, 0, &addr, &size); 103 if (error) { 104 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 105 return; 106 } 107 108 if (bus_space_map(sc->sc_iot, addr, size, 0, 109 &sc->sc_ioh)) { 110 aprint_error_dev(sc->sc_dev, "unable to map device\n"); 111 return; 112 } 113 114 /* discard initial numbers, broadcom says they are "less random" */ 115 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000); 116 117 /* enable rng */ 118 ctrl = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL); 119 ctrl |= RNG_CTRL_EN; 120 bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl); 121 122 /* set up an rndsource */ 123 rndsource_setcb(&sc->sc_rndsource, &bcmrng_get, sc); 124 rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG, 125 RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB); 126 } 127 128 static void 129 bcmrng_get(size_t bytes_wanted, void *arg) 130 { 131 struct bcm2835rng_softc *sc = arg; 132 uint32_t status, cnt; 133 uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */ 134 135 while (bytes_wanted) { 136 status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS); 137 cnt = __SHIFTOUT(status, RNG_STATUS_CNT); 138 KASSERT(cnt < RNG_DATA_MAX); 139 if (cnt == 0) 140 continue; /* XXX Busy-waiting seems wrong... */ 141 bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf, 142 cnt); 143 rnd_add_data_sync(&sc->sc_rndsource, buf, (cnt * 4), 144 (cnt * 4 * NBBY)); 145 bytes_wanted -= MIN(bytes_wanted, (cnt * 4)); 146 } 147 explicit_memset(buf, 0, sizeof(buf)); 148 } 149