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 29 #include <stand.h> 30 #include <btxv86.h> 31 #include "bootstrap.h" 32 #include "libi386.h" 33 34 time_t getsecs(void); 35 static int bios_seconds(void); 36 37 /* 38 * Return the BIOS time-of-day value. 39 * 40 * XXX uses undocumented BCD support from libstand. 41 */ 42 static int 43 bios_seconds(void) 44 { 45 int hr, minute, sec; 46 47 v86.ctl = 0; 48 v86.addr = 0x1a; /* int 0x1a, function 2 */ 49 v86.eax = 0x0200; 50 v86int(); 51 52 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */ 53 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */ 54 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */ 55 56 return (hr * 3600 + minute * 60 + sec); 57 } 58 59 /* 60 * Return the time in seconds since the beginning of the day. 61 * 62 * Some BIOSes (notably qemu) don't correctly read the RTC 63 * registers in an atomic way, sometimes returning bogus values. 64 * Therefore we "debounce" the reading by accepting it only when 65 * we got 8 identical values in succession. 66 * 67 * If we pass midnight, don't wrap back to 0. 68 */ 69 time_t 70 time(time_t *t) 71 { 72 static time_t lasttime; 73 time_t now, check; 74 int same, try; 75 76 same = try = 0; 77 check = bios_seconds(); 78 do { 79 now = check; 80 check = bios_seconds(); 81 if (check != now) 82 same = 0; 83 } while (++same < 8 && ++try < 1000); 84 85 if (now < lasttime) 86 now += 24 * 3600; 87 lasttime = now; 88 89 if (t != NULL) 90 *t = now; 91 return(now); 92 } 93 94 time_t 95 getsecs(void) 96 { 97 time_t n = 0; 98 time(&n); 99 return n; 100 } 101 102 /* 103 * Use the BIOS Wait function to pause for (period) microseconds. 104 * 105 * Resolution of this function is variable, but typically around 106 * 1ms. 107 */ 108 void 109 delay(int period) 110 { 111 v86.ctl = 0; 112 v86.addr = 0x15; /* int 0x15, function 0x86 */ 113 v86.eax = 0x8600; 114 v86.ecx = period >> 16; 115 v86.edx = period & 0xffff; 116 v86int(); 117 } 118