|
|
/*-------------------------------------------------------------------------+
| timer.c v1.1 - PC386 BSP - 1997/08/07
+--------------------------------------------------------------------------+
| This file contains the PC386 timer package.
+--------------------------------------------------------------------------+
| NOTE: It is important that the timer start/stop overhead be determined
| when porting or modifying this code.
+--------------------------------------------------------------------------+
| (C) Copyright 1997 -
| - NavIST Group - Real-Time Distributed Systems and Industrial Automation
|
| http://pandora.ist.utl.pt
|
| Instituto Superior Tecnico * Lisboa * PORTUGAL
+--------------------------------------------------------------------------+
| Disclaimer:
|
| This file is provided "AS IS" without warranty of any kind, either
| expressed or implied.
+--------------------------------------------------------------------------+
| This code is base on:
| timer.c,v 1.7 1995/12/19 20:07:43 joel Exp - go32 BSP
| With the following copyright notice:
| **************************************************************************
| * 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 found in the file LICENSE in this distribution or at
| * http://www.OARcorp.com/rtems/license.html.
| **************************************************************************
|
| $Id$
+--------------------------------------------------------------------------*/
#include <stdlib.h>
#include <bsp.h>
#include <irq.h>
/*-------------------------------------------------------------------------+
| Constants
+--------------------------------------------------------------------------*/
#define TIMER_IRQ 0x00 /* Timer IRQ. */
#define AVG_OVERHEAD 0 /* 0.1 microseconds to start/stop timer. */
#define LEAST_VALID 1 /* Don't trust a value lower than this. */
/*-------------------------------------------------------------------------+
| Global Variables
+--------------------------------------------------------------------------*/
volatile rtems_unsigned32 Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead = TRUE;
/*-------------------------------------------------------------------------+
| Pentium optimized timer handling.
+--------------------------------------------------------------------------*/
#if defined(pentium)
/*-------------------------------------------------------------------------+
| Function: rdtsc
| Description: Read the value of PENTIUM on-chip cycle counter.
| Global Variables: None.
| Arguments: None.
| Returns: Value of PENTIUM on-chip cycle counter.
+--------------------------------------------------------------------------*/
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;
} /* rdtsc */
/*-------------------------------------------------------------------------+
| Function: Timer_exit
| Description: Timer cleanup routine at RTEMS exit. NOTE: This routine is
| not really necessary, since there will be a reset at exit.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_exit(void)
{
PC386_disableIrq(TIMER_IRQ);
} /* Timer_exit */
/*-------------------------------------------------------------------------+
| Function: Timer_initialize
| Description: Timer initialization routine.
| Global Variables: Ttimer_val.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_initialize(void)
{
static rtems_boolean First = TRUE;
if (First)
{
First = FALSE;
atexit(Timer_exit); /* Try not to hose the system at exit. */
PC386_enableIrq(TIMER_IRQ);
/* Disable the programmable timer so ticks don't interfere. */
}
Ttimer_val = rdtsc(); /* read starting time */
} /* Timer_initialize */
/*-------------------------------------------------------------------------+
| Function: Read_timer
| Description: Read hardware timer value.
| Global Variables: Ttimer_val, Timer_driver_Find_average_overhead.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_unsigned32
Read_timer(void)
{
register rtems_unsigned32 total;
total = (rtems_unsigned32)(rdtsc() - Ttimer_val);
if (Timer_driver_Find_average_overhead)
return total;
else if (total < LEAST_VALID)
return 0; /* below timer resolution */
else
return (total - AVG_OVERHEAD);
} /* Read_timer */
#else /* pentium */
/*-------------------------------------------------------------------------+
| Non-Pentium timer handling.
+--------------------------------------------------------------------------*/
#define US_PER_ISR 250 /* Number of micro-seconds per timer interruption */
/*-------------------------------------------------------------------------+
| External Prototypes
+--------------------------------------------------------------------------*/
extern rtems_isr timerisr(rtems_vector_number);
/* timer (int 08h) Interrupt Service Routine (defined in 'timerisr.s') */
/*-------------------------------------------------------------------------+
| Function: Timer_exit
| Description: Timer cleanup routine at RTEMS exit. NOTE: This routine is
| not really necessary, since there will be a reset at exit.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_exit(void)
{
/* reset timer mode to standard (DOS) value */
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, 0);
outport_byte(TIMER_CNTR0, 0);
} /* Timer_exit */
/*-------------------------------------------------------------------------+
| Function: Timer_initialize
| Description: Timer initialization routine.
| Global Variables: Ttimer_val.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_initialize(void)
{
static rtems_boolean First = TRUE;
if (First)
{
First = FALSE;
atexit(Timer_exit); /* Try not to hose the system at exit. */
/* install a raw interrupt handler for timer */
PC386_installRawIrqHandler(TIMER_IRQ, timerisr);
/* 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);
}
/* wait for ISR to be called at least once */
Ttimer_val = 0;
while (Ttimer_val == 0)
continue;
Ttimer_val = 0;
} /* Timer_initialize */
/*-------------------------------------------------------------------------+
| Function: Read_timer
| Description: Read hardware timer value.
| Global Variables: Ttimer_val, Timer_driver_Find_average_overhead.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_unsigned32
Read_timer(void)
{
register rtems_unsigned32 total, clicks;
register rtems_unsigned8 lsb, msb;
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));
if (Timer_driver_Find_average_overhead)
return total;
else if (total < LEAST_VALID)
return 0; /* below timer resolution */
else
return (total - AVG_OVERHEAD);
}
#endif /* pentium */
/*-------------------------------------------------------------------------+
| Function: Empty_function
| Description: Empty function used in time tests.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_status_code Empty_function(void)
{
return RTEMS_SUCCESSFUL;
} /* Empty function */
/*-------------------------------------------------------------------------+
| Function: Set_find_average_overhead
| Description: Set internal Timer_driver_Find_average_overhead flag value.
| Global Variables: Timer_driver_Find_average_overhead.
| Arguments: find_flag - new value of the flag.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Set_find_average_overhead(rtems_boolean find_flag)
{
Timer_driver_Find_average_overhead = find_flag;
} /* Set_find_average_overhead */
|
