1 /*- 2 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD: src/sys/boot/i386/libi386/time.c,v 1.5 2003/08/25 23:28:31 obrien Exp $ 27 * $DragonFly: src/sys/boot/pc32/libi386/time.c,v 1.3 2003/11/10 06:08:36 dillon Exp $ 28 */ 29 #include <stand.h> 30 #include <btxv86.h> 31 #include "bootstrap.h" 32 #include "libi386.h" 33 34 /* 35 * Return the time in seconds since the beginning of the day. 36 * 37 * If we pass midnight, don't wrap back to 0. 38 * 39 * XXX uses undocumented BCD support from libstand. 40 */ 41 static int 42 bios_seconds(void) 43 { 44 time_t now; 45 int sec; 46 int minute; 47 int hr; 48 49 v86.ctl = 0; 50 v86.addr = 0x1a; /* int 0x1a, function 2 */ 51 v86.eax = 0x0200; 52 v86int(); 53 54 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */ 55 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */ 56 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */ 57 now = hr * 3600 + minute * 60 + sec; 58 59 return (now); 60 } 61 62 /* 63 * Some BIOSes (notably qemu) don't correctly read the RTC 64 * registers in an atomic way, sometimes returning bogus values. 65 * Therefore we "debounce" the reading by accepting it only when 66 * we got 8 identical values in succession. 67 * 68 * If we pass midnight, don't wrap back to 0. 69 */ 70 time_t 71 time(time_t *t) 72 { 73 static time_t lasttime; 74 time_t now, check; 75 int same, try; 76 77 try = same = 0; 78 check = bios_seconds(); 79 do { 80 now = check; 81 check = bios_seconds(); 82 if (check != now) 83 same = 0; 84 } while (++same < 8 && ++try < 1000); 85 86 if (now < lasttime) 87 now += 24 * 3600; 88 lasttime = now; 89 90 if (t != NULL) 91 *t = now; 92 return(now); 93 } 94 95 /* 96 * Use the BIOS Wait function to pause for (period) microseconds. 97 * 98 * Resolution of this function is variable, but typically around 99 * 1ms. 100 */ 101 void 102 delay(int period) 103 { 104 v86.ctl = 0; 105 v86.addr = 0x15; /* int 0x15, function 0x86 */ 106 v86.eax = 0x8600; 107 v86.ecx = period >> 16; 108 v86.edx = period & 0xffff; 109 v86int(); 110 } 111