blob: f170a3d5868c02d17d825994e6f569fde537cf27 (
plain) (
tree)
|
|
/* Timer_init()
*
* This routine initializes the timer on the IBM 386.
*
* Input parameters: NONE
*
* Output parameters: NONE
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* COPYRIGHT (c) 1989-1997.
* On-Line Applications Research Corporation (OAR).
* Copyright assigned to U.S. Government, 1994.
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
volatile rtems_unsigned32 Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead;
#if defined(pentium)
static inline unsigned long long rdtsc( void )
{
/* Return the value of the on-chip cycle counter. */
unsigned long long result;
__asm __volatile( ".byte 0x0F, 0x31" : "=A" (result) );
return result;
}
#else
#define US_PER_ISR 250
extern rtems_isr timerisr();
static rtems_isr_entry Old_Ticker;
#endif
static void Timer_exit( void )
{
#if defined(pentium)
CLOCK_ENABLE();
#else /* pentium */
extern void rtc_set_dos_date( void );
/* reset to DOS value: */
outport_byte( TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN );
outport_byte( TIMER_CNTR0, 0 );
outport_byte( TIMER_CNTR0, 0 );
/* reset time-of-day */
rtc_set_dos_date();
/* re-enable old handler: assume it was one of ours */
set_vector( (rtems_isr_entry)Old_Ticker, 0x8, 0 );
#endif /* pentium */
}
void Timer_initialize()
{
extern int atexit( void (*)(void) );
static int First = 1;
if ( First ) {
First = 0;
/* Try not to hose the system on return to DOS. */
atexit( Timer_exit );
#if defined(pentium)
/* Disable the programmable timer so ticks don't interfere. */
CLOCK_DISABLE();
#else /* pentium */
/* install a timer ISR */
Old_Ticker = (rtems_isr_entry) set_vector( timerisr, 0x8, 0 );
/* Wait for ISR to be called at least once */
Ttimer_val = 0;
while ( Ttimer_val == 0 )
continue;
/* load timer for US_PER_ISR microsecond period */
outport_byte( TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN );
outport_byte( TIMER_CNTR0, US_TO_TICK(US_PER_ISR) >> 0 & 0xff );
outport_byte( TIMER_CNTR0, US_TO_TICK(US_PER_ISR) >> 8 & 0xff );
#endif /* PENTIUM */
}
#if defined(pentium)
Ttimer_val = rdtsc(); /* read starting time */
#else
/* Wait for ISR to be called at least once */
asm( "sti" );
Ttimer_val = 0;
while ( Ttimer_val == 0 )
continue;
Ttimer_val = 0;
#endif
}
#define AVG_OVERHEAD 0 /* 0.1 microseconds to start/stop timer. */
#define LEAST_VALID 1 /* Don't trust a value lower than this */
int Read_timer()
{
register rtems_unsigned32 total;
#if defined(pentium)
total = rdtsc() - Ttimer_val;
#else /* pentium */
register rtems_unsigned8 lsb, msb;
register rtems_unsigned32 clicks;
outport_byte( TIMER_MODE, TIMER_SEL0|TIMER_LATCH );
inport_byte( TIMER_CNTR0, lsb );
inport_byte( TIMER_CNTR0, msb );
clicks = msb << 8 | lsb;
total = (Ttimer_val * US_PER_ISR) + (US_PER_ISR - TICK_TO_US( clicks ));
#endif /* pentium */
if ( Timer_driver_Find_average_overhead == 1 )
return total;
else if ( total < LEAST_VALID )
return 0; /* below timer resolution */
else
return total - AVG_OVERHEAD;
}
rtems_status_code Empty_function( void )
{
return RTEMS_SUCCESSFUL;
}
void Set_find_average_overhead(
rtems_boolean find_flag
)
{
Timer_driver_Find_average_overhead = find_flag;
}
|