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 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 30 #include <stand.h> 31 #include <btxv86.h> 32 #include "bootstrap.h" 33 #include "libi386.h" 34 35 time_t getsecs(void); 36 static int bios_seconds(void); 37 38 /* 39 * Return the BIOS time-of-day value. 40 * 41 * XXX uses undocumented BCD support from libsa. 42 */ 43 static int 44 bios_seconds(void) 45 { 46 int hr, minute, sec; 47 48 v86.ctl = 0; 49 v86.addr = 0x1a; /* int 0x1a, function 2 */ 50 v86.eax = 0x0200; 51 v86int(); 52 53 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */ 54 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */ 55 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */ 56 57 return (hr * 3600 + minute * 60 + sec); 58 } 59 60 /* 61 * Return the time in seconds since the beginning of the day. 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 same = try = 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 time_t 96 getsecs(void) 97 { 98 time_t n = 0; 99 time(&n); 100 return n; 101 } 102 103 /* 104 * Use the BIOS Wait function to pause for (period) microseconds. 105 * 106 * Resolution of this function is variable, but typically around 107 * 1ms. 108 */ 109 void 110 delay(int period) 111 { 112 v86.ctl = 0; 113 v86.addr = 0x15; /* int 0x15, function 0x86 */ 114 v86.eax = 0x8600; 115 v86.ecx = period >> 16; 116 v86.edx = period & 0xffff; 117 v86int(); 118 } 119