1 /* 2 * Copyright (C) 2008 Michael Brown <mbrown (at) fensystems.co.uk>. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License as 6 * published by the Free Software Foundation; either version 2 of the 7 * License, or any later version. 8 * 9 * This program is distributed in the hope that it will be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 17 */ 18 19 FILE_LICENCE ( GPL2_OR_LATER ); 20 21 /** @file 22 * 23 * BIOS timer 24 * 25 */ 26 27 #include <gpxe/timer.h> 28 #include <realmode.h> 29 #include <bios.h> 30 31 /** 32 * Get current system time in ticks 33 * 34 * @ret ticks Current time, in ticks 35 * 36 * Use direct memory access to BIOS variables, longword 0040:006C 37 * (ticks today) and byte 0040:0070 (midnight crossover flag) instead 38 * of calling timeofday BIOS interrupt. 39 */ 40 static unsigned long bios_currticks ( void ) { 41 static int days = 0; 42 uint32_t ticks; 43 uint8_t midnight; 44 45 /* Re-enable interrupts so that the timer interrupt can occur */ 46 __asm__ __volatile__ ( REAL_CODE ( "sti\n\t" 47 "nop\n\t" 48 "nop\n\t" 49 "cli\n\t" ) : : ); 50 51 get_real ( ticks, BDA_SEG, 0x006c ); 52 get_real ( midnight, BDA_SEG, 0x0070 ); 53 54 if ( midnight ) { 55 midnight = 0; 56 put_real ( midnight, BDA_SEG, 0x0070 ); 57 days += 0x1800b0; 58 } 59 60 return ( days + ticks ); 61 } 62 63 PROVIDE_TIMER_INLINE ( pcbios, udelay ); 64 PROVIDE_TIMER ( pcbios, currticks, bios_currticks ); 65 PROVIDE_TIMER_INLINE ( pcbios, ticks_per_sec ); 66
