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