90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
/*
|
|
* 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., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
* 02110-1301, USA.
|
|
*
|
|
* You can also choose to distribute this program under the terms of
|
|
* the Unmodified Binary Distribution Licence (as given in the file
|
|
* COPYING.UBDL), provided that you have satisfied its requirements.
|
|
*/
|
|
|
|
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
|
|
|
|
/** @file
|
|
*
|
|
* BIOS timer
|
|
*
|
|
*/
|
|
|
|
#include <ipxe/timer.h>
|
|
#include <realmode.h>
|
|
#include <bios.h>
|
|
#include <ipxe/pit8254.h>
|
|
|
|
/** Number of ticks per day
|
|
*
|
|
* This seems to be the normative value, as used by e.g. SeaBIOS to
|
|
* decide when to set the midnight rollover flag.
|
|
*/
|
|
#define BIOS_TICKS_PER_DAY 0x1800b0
|
|
|
|
/** Number of ticks per BIOS tick */
|
|
#define TICKS_PER_BIOS_TICK \
|
|
( ( TICKS_PER_SEC * 60 * 60 * 24 ) / BIOS_TICKS_PER_DAY )
|
|
|
|
/**
|
|
* 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 uint32_t offset;
|
|
uint32_t ticks;
|
|
uint8_t midnight;
|
|
|
|
/* Re-enable interrupts so that the timer interrupt can occur */
|
|
__asm__ __volatile__ ( "sti\n\t"
|
|
"nop\n\t"
|
|
"nop\n\t"
|
|
"cli\n\t" );
|
|
|
|
/* Read current BIOS time of day */
|
|
get_real ( ticks, BDA_SEG, BDA_TICKS );
|
|
get_real ( midnight, BDA_SEG, BDA_MIDNIGHT );
|
|
|
|
/* Handle midnight rollover */
|
|
if ( midnight ) {
|
|
midnight = 0;
|
|
put_real ( midnight, BDA_SEG, BDA_MIDNIGHT );
|
|
offset += BIOS_TICKS_PER_DAY;
|
|
}
|
|
ticks += offset;
|
|
|
|
/* Convert to timer ticks */
|
|
return ( ticks * TICKS_PER_BIOS_TICK );
|
|
}
|
|
|
|
/** BIOS timer */
|
|
struct timer bios_timer __timer ( TIMER_NORMAL ) = {
|
|
.name = "bios",
|
|
.currticks = bios_currticks,
|
|
.udelay = pit8254_udelay,
|
|
};
|