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/* timer.c
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*
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* This file manages the benchmark timer used by the RTEMS Timing Test Suite.
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* Each measured time period is demarcated by calls to Timer_initialize() and
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* Read_timer(). Read_timer() usually returns the number of microseconds
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* since Timer_initialize() exitted.
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*
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* These functions are prototyped in rtems/c/src/lib/include/timerdrv.h and
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* must be implemented as part of the BSP.
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*
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* This port does not allow the application to select which timer on the
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* MVME167 to use for the timer, nor does it allow the application to
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* configure the timer. The timer uses the VMEchip2 Tick Timer #1. This timer
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* is distinct from the clock, which uses Tick Timer #2 in the VMEchip2.
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*
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* All page references are to the MVME166/MVME167/MVME187 Single Board
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* Computer Programmer's Reference Guide (MVME187PG/D2) with the April 1993
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* supplements/addenda (MVME187PG/D2A1).
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.OARcorp.com/rtems/license.html.
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*
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* Modifications of respective RTEMS file:
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* Copyright (c) 1998, National Research Council of Canada
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*
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* $Id: timer.c,v 1.2 2001-09-27 12:00:20 chris Exp $
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*/
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#include <rtems.h>
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#include <bsp.h>
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/* Periodic tick interval */
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#define TICK_INTERVAL 10000UL /* T1's countdown constant (10 ms) */
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#define TIMER_INT_LEVEL 6 /* T1's interrupt level */
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#define TIMER_VECTOR (VBR0 * 0x10 + 0x8) /* T1 is vector $X8 (p. 2-71)*/
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/* Number of interrupts since timer was re-initialized */
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rtems_unsigned32 Ttimer_val;
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/*
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* Set to TRUE to return raw value. Normally zero. Depends on being allocated
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* in the .bss section and on that section being explicitly zeroed at boot
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* time.
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*/
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rtems_boolean Timer_driver_Find_average_overhead;
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rtems_isr timerisr();
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/*
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* This routine initializes the Tick Timer 1 on the MVME167 board.
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*
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* Input parameters: NONE
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*
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* Output parameters: NONE
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*
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* NOTE: This routine may not work if the optimizer is enabled for some
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* compilers. The multiple writes may be optimized away.
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*
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* It is important that the timer start/stop overhead be
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* determined when porting or modifying this code.
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*
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* THE VMECHIP2 PRESCALER REGISTER IS ASSUMED TO BE SET!
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* The prescaler is used by all VMEchip2 timers, including the VMEbus grant
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* timeout counter, the DMAC time off timer, the DMAC timer on timer, and the
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* VMEbus global timeout timer. The prescaler value is normally set by the
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* boot ROM to provide a 1 MHz clock to the timers. For a 25 MHz MVME167, the
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* prescaler value should be 0xE7 (page 2-63).
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*/
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void Timer_initialize()
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{
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(void) set_vector( timerisr, TIMER_VECTOR, 0 );
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Ttimer_val = 0; /* clear timer ISR count */
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lcsr->intr_ena &= 0xFEFFFFFF; /* disable tick timer 1 interrupt */
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lcsr->intr_clear |= 0x01000000; /* clear tick timer 1 interrupt */
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lcsr->intr_level[0] = /* set int level */
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(lcsr->intr_level[0] & 0xFFFFFFF0) | TIMER_INT_LEVEL;
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lcsr->timer_cmp_1 = TICK_INTERVAL; /* period in compare register */
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lcsr->timer_cnt_1 = 0; /* clear tick timer 1 counter */
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lcsr->board_ctl |= 7; /* start tick timer 1, reset-on-compare, */
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/* and clear overflow counter */
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lcsr->intr_ena |= 0x01000000; /* enable tick timer 1 interrupt */
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lcsr->vector_base |= MASK_INT; /* unmask VMEchip2 interrupts */
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}
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#define AVG_OVERHEAD 3UL /* It typically takes 3.0 microseconds */
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/* (3 countdowns) to start/stop the timer. */
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#define LEAST_VALID 3UL /* Don't trust a value lower than this */
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/*
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* This routine reads the Tick Timer 1 on the MVME167 board.
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*
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* Input parameters: NONE
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*
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* Output parameters: time in microseconds
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*
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* AVG_OVEREHAD is the overhead for starting and stopping the timer. It
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* is usually deducted from the number returned.
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*
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* LEAST_VALID is the lowest number this routine should trust. Numbers
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* below this are "noise" and zero is returned.
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*/
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int Read_timer()
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{
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rtems_unsigned32 total;
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total = (Ttimer_val * TICK_INTERVAL) + lcsr->timer_cnt_1;
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if ( Timer_driver_Find_average_overhead )
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return total; /* in one microsecond units */
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if ( total < LEAST_VALID )
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return 0; /* below timer resolution */
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return total - AVG_OVERHEAD;
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}
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/*
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* Empty function call used in loops to measure basic cost of looping
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* in Timing Test Suite.
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*
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* Input parameters: NONE
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*
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* Output parameters: time in microseconds
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*/
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rtems_status_code Empty_function( void )
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{
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return RTEMS_SUCCESSFUL;
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}
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/*
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* This routine sets the Timer_driver_Find_average_overhead flag in this
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* module.
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*
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* Input parameters: NONE
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*
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* Output parameters: time in microseconds
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*/
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void Set_find_average_overhead(
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rtems_boolean find_flag
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)
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{
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Timer_driver_Find_average_overhead = find_flag;
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}
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