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 /**
  * @file
  *
  * This file manages the benchmark timer used by the RTEMS Timing Test Suite.
  * Each measured time period is demarcated by calls to
  * benchmark_timer_initialize() and benchmark_timer_read().
  * benchmark_timer_read() usually returns the number of microseconds
  * since benchmark_timer_initialize() exitted.
  *
  * These functions are prototyped in rtems/btimer.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.rtems.org/license/LICENSE.
  *
  *  Modifications of respective RTEMS file:
  *  Copyright (c) 1998, National Research Council of Canada
  */
 
 #include <rtems.h>
 #include <rtems/btimer.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 */
 uint32_t            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.
  */
 bool benchmark_timer_find_average_overhead;
 
 rtems_isr timerisr(rtems_vector_number);
 
 /*
  *  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 benchmark_timer_initialize(void)
 {
   (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.
  */
 benchmark_timer_t benchmark_timer_read(void)
 {
   uint32_t            total;
 
   total = (Ttimer_val * TICK_INTERVAL) + lcsr->timer_cnt_1;
 
   if ( benchmark_timer_find_average_overhead )
     return total;          /* in one microsecond units */
 
   if ( total < LEAST_VALID )
     return 0;            /* below timer resolution */
 
   return total - AVG_OVERHEAD;
 }
 
 /*
  *  This routine sets the benchmark_timer_find_average_overhead flag in this
  *  module.
  *
  *  Input parameters:  NONE
  *
  *  Output parameters:  time in microseconds
  */
 void benchmark_timer_disable_subtracting_average_overhead(
   bool find_flag
 )
 {
   benchmark_timer_find_average_overhead = find_flag;
 }

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