1 /* $NetBSD: amdccp.c,v 1.2 2020/04/30 03:40:53 riastradh Exp $ */ 2 3 /* 4 * Copyright (c) 2018 Jonathan A. Kollasch 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 20 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 21 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 25 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 26 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 31 __KERNEL_RCSID(0, "$NetBSD: amdccp.c,v 1.2 2020/04/30 03:40:53 riastradh Exp $"); 32 33 #include <sys/param.h> 34 #include <sys/systm.h> 35 #include <sys/device.h> 36 #include <sys/bus.h> 37 #include <sys/rndsource.h> 38 39 #include <dev/ic/amdccpvar.h> 40 41 static uint32_t amdccp_rnd_read(struct amdccp_softc *); 42 static void amdccp_rnd_callback(size_t, void *); 43 44 void 45 amdccp_common_attach(struct amdccp_softc *sc) 46 { 47 mutex_init(&sc->sc_rndlock, MUTEX_DEFAULT, IPL_VM); 48 rndsource_setcb(&sc->sc_rndsource, amdccp_rnd_callback, sc); 49 rnd_attach_source(&sc->sc_rndsource, device_xname(sc->sc_dev), 50 RND_TYPE_RNG, RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB); 51 } 52 53 static uint32_t 54 amdccp_rnd_read(struct amdccp_softc *sc) 55 { 56 size_t retries = 5; 57 uint32_t bits; 58 59 /* TRNG register reads 0x0 when bits aren't valid */ 60 while (retries--) { 61 bits = bus_space_read_4(sc->sc_bst, sc->sc_bsh, CCP_TRNG_REG); 62 if (bits != 0x0) 63 break; 64 } 65 66 return bits; 67 } 68 69 static void 70 amdccp_rnd_callback(size_t bytes_wanted, void *priv) 71 { 72 struct amdccp_softc * const sc = priv; 73 uint32_t buf[128]; 74 size_t cnt; 75 76 mutex_enter(&sc->sc_rndlock); 77 while (bytes_wanted) { 78 const size_t nbytes = MIN(bytes_wanted, sizeof(buf)); 79 const size_t nwords = howmany(nbytes, sizeof(buf[0])); 80 for (cnt = 0; cnt < nwords; cnt++) { 81 buf[cnt] = amdccp_rnd_read(sc); 82 if (buf[cnt] == 0) { 83 break; 84 } 85 } 86 const size_t cntby = cnt * sizeof(buf[0]); 87 rnd_add_data_sync(&sc->sc_rndsource, buf, cntby, cntby * NBBY); 88 bytes_wanted -= MIN(bytes_wanted, cntby); 89 } 90 explicit_memset(buf, 0, sizeof(buf)); 91 mutex_exit(&sc->sc_rndlock); 92 } 93