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/*
* Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
/** @file
*
* BIOS timer
*
*/
#include <gpxe/timer.h>
#include <realmode.h>
#include <bios.h>
/**
* Get current system time in ticks
*
* @ret ticks Current time, in ticks
*
* Use direct memory access to BIOS variables, longword 0040:006C
* (ticks today) and byte 0040:0070 (midnight crossover flag) instead
* of calling timeofday BIOS interrupt.
*/
static unsigned long bios_currticks ( void ) {
static int days = 0;
uint32_t ticks;
uint8_t midnight;
/* Re-enable interrupts so that the timer interrupt can occur */
__asm__ __volatile__ ( REAL_CODE ( "sti\n\t"
"nop\n\t"
"nop\n\t"
"cli\n\t" ) : : );
get_real ( ticks, BDA_SEG, 0x006c );
get_real ( midnight, BDA_SEG, 0x0070 );
if ( midnight ) {
midnight = 0;
put_real ( midnight, BDA_SEG, 0x0070 );
days += 0x1800b0;
}
return ( days + ticks );
}
PROVIDE_TIMER_INLINE ( pcbios, udelay );
PROVIDE_TIMER ( pcbios, currticks, bios_currticks );
PROVIDE_TIMER_INLINE ( pcbios, ticks_per_sec );
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