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 <stand.h> 28 #include <btxv86.h> 29 #include "bootstrap.h" 30 #include "libi386.h" 31 32 time_t getsecs(void); 33 static int bios_seconds(void); 34 35 /* 36 * Return the BIOS time-of-day value. 37 * 38 * XXX uses undocumented BCD support from libsa. 39 */ 40 static int 41 bios_seconds(void) 42 { 43 int hr, minute, sec; 44 45 v86.ctl = 0; 46 v86.addr = 0x1a; /* int 0x1a, function 2 */ 47 v86.eax = 0x0200; 48 v86int(); 49 50 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */ 51 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */ 52 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */ 53 54 return (hr * 3600 + minute * 60 + sec); 55 } 56 57 /* 58 * Return the time in seconds since the beginning of the day. 59 * 60 * Some BIOSes (notably qemu) don't correctly read the RTC 61 * registers in an atomic way, sometimes returning bogus values. 62 * Therefore we "debounce" the reading by accepting it only when 63 * we got 8 identical values in succession. 64 * 65 * If we pass midnight, don't wrap back to 0. 66 */ 67 time_t 68 time(time_t *t) 69 { 70 static time_t lasttime; 71 time_t now, check; 72 int same, try; 73 74 same = try = 0; 75 check = bios_seconds(); 76 do { 77 now = check; 78 check = bios_seconds(); 79 if (check != now) 80 same = 0; 81 } while (++same < 8 && ++try < 1000); 82 83 if (now < lasttime) 84 now += 24 * 3600; 85 lasttime = now; 86 87 if (t != NULL) 88 *t = now; 89 return(now); 90 } 91 92 time_t 93 getsecs(void) 94 { 95 time_t n = 0; 96 time(&n); 97 return n; 98 } 99 100 /* 101 * Use the BIOS Wait function to pause for (period) microseconds. 102 * 103 * Resolution of this function is variable, but typically around 104 * 1ms. 105 */ 106 void 107 delay(int period) 108 { 109 v86.ctl = 0; 110 v86.addr = 0x15; /* int 0x15, function 0x86 */ 111 v86.eax = 0x8600; 112 v86.ecx = period >> 16; 113 v86.edx = period & 0xffff; 114 v86int(); 115 } 116