bios_timer.c File Reference

BIOS timer. More...

#include <gpxe/timer.h>
#include <realmode.h>
#include <bios.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER)
static unsigned long	bios_currticks (void)
	Get current system time in ticks.
	PROVIDE_TIMER_INLINE (pcbios, udelay)
	PROVIDE_TIMER (pcbios, currticks, bios_currticks)
	PROVIDE_TIMER_INLINE (pcbios, ticks_per_sec)

---

Detailed Description

BIOS timer.

Definition in file bios_timer.c.

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static unsigned long bios_currticks

(

void

)

[static]

Get current system time in ticks.

Return values:

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.

Definition at line 40 of file bios_timer.c.

References __asm__(), BDA_SEG, get_real, put_real, and REAL_CODE.

                                             {
        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
	)