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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., 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,
- };
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