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/* timer.c
*
* This file manages the benchmark timer used by the RTEMS Timing Test Suite.
* Each measured time period is demarcated by calls to Timer_initialize() and
* Read_timer(). Read_timer() usually returns the number of microseconds
* since Timer_initialize() exitted.
*
* These functions are prototyped in rtems/c/src/lib/include/timerdrv.h and
* must be implemented as part of the BSP.
*
* This port does not allow the application to select which timer on the
* MVME167 to use for the timer, nor does it allow the application to
* configure the timer. The timer uses the VMEchip2 Tick Timer #1. This timer
* is distinct from the clock, which uses Tick Timer #2 in the VMEchip2.
*
* All page references are to the MVME166/MVME167/MVME187 Single Board
* Computer Programmer's Reference Guide (MVME187PG/D2) with the April 1993
* supplements/addenda (MVME187PG/D2A1).
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* 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.
*
* Modifications of respective RTEMS file:
* Copyright (c) 1998, National Research Council of Canada
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
/* Periodic tick interval */
#define TICK_INTERVAL 10000UL /* T1's countdown constant (10 ms) */
#define TIMER_INT_LEVEL 6 /* T1's interrupt level */
#define TIMER_VECTOR (VBR0 * 0x10 + 0x8) /* T1 is vector $X8 (p. 2-71)*/
/* Number of interrupts since timer was re-initialized */
rtems_unsigned32 Ttimer_val;
/*
* Set to TRUE to return raw value. Normally zero. Depends on being allocated
* in the .bss section and on that section being explicitly zeroed at boot
* time.
*/
rtems_boolean Timer_driver_Find_average_overhead;
rtems_isr timerisr();
/*
* This routine initializes the Tick Timer 1 on the MVME167 board.
*
* Input parameters: NONE
*
* Output parameters: NONE
*
* NOTE: This routine may not work if the optimizer is enabled for some
* compilers. The multiple writes may be optimized away.
*
* It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* THE VMECHIP2 PRESCALER REGISTER IS ASSUMED TO BE SET!
* The prescaler is used by all VMEchip2 timers, including the VMEbus grant
* timeout counter, the DMAC time off timer, the DMAC timer on timer, and the
* VMEbus global timeout timer. The prescaler value is normally set by the
* boot ROM to provide a 1 MHz clock to the timers. For a 25 MHz MVME167, the
* prescaler value should be 0xE7 (page 2-63).
*/
void Timer_initialize()
{
(void) set_vector( timerisr, TIMER_VECTOR, 0 );
Ttimer_val = 0; /* clear timer ISR count */
lcsr->intr_ena &= 0xFEFFFFFF; /* disable tick timer 1 interrupt */
lcsr->intr_clear |= 0x01000000; /* clear tick timer 1 interrupt */
lcsr->intr_level[0] = /* set int level */
(lcsr->intr_level[0] & 0xFFFFFFF0) | TIMER_INT_LEVEL;
lcsr->timer_cmp_1 = TICK_INTERVAL; /* period in compare register */
lcsr->timer_cnt_1 = 0; /* clear tick timer 1 counter */
lcsr->board_ctl |= 7; /* start tick timer 1, reset-on-compare, */
/* and clear overflow counter */
lcsr->intr_ena |= 0x01000000; /* enable tick timer 1 interrupt */
lcsr->vector_base |= MASK_INT; /* unmask VMEchip2 interrupts */
}
#define AVG_OVERHEAD 3UL /* It typically takes 3.0 microseconds */
/* (3 countdowns) to start/stop the timer. */
#define LEAST_VALID 3UL /* Don't trust a value lower than this */
/*
* This routine reads the Tick Timer 1 on the MVME167 board.
*
* Input parameters: NONE
*
* Output parameters: time in microseconds
*
* AVG_OVEREHAD is the overhead for starting and stopping the timer. It
* is usually deducted from the number returned.
*
* LEAST_VALID is the lowest number this routine should trust. Numbers
* below this are "noise" and zero is returned.
*/
int Read_timer()
{
rtems_unsigned32 total;
total = (Ttimer_val * TICK_INTERVAL) + lcsr->timer_cnt_1;
if ( Timer_driver_Find_average_overhead )
return total; /* in one microsecond units */
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
return total - AVG_OVERHEAD;
}
/*
* Empty function call used in loops to measure basic cost of looping
* in Timing Test Suite.
*
* Input parameters: NONE
*
* Output parameters: time in microseconds
*/
rtems_status_code Empty_function( void )
{
return RTEMS_SUCCESSFUL;
}
/*
* This routine sets the Timer_driver_Find_average_overhead flag in this
* module.
*
* Input parameters: NONE
*
* Output parameters: time in microseconds
*/
void Set_find_average_overhead(
rtems_boolean find_flag
)
{
Timer_driver_Find_average_overhead = find_flag;
}
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