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106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
/* timer.c
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*
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* This file implements a benchmark timer using the General Purpose Timer on
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* the MEC.
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*
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* COPYRIGHT (c) 1989-1998.
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* On-Line Applications Research Corporation (OAR).
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* Copyright assigned to U.S. Government, 1994.
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*
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* The license and distribution terms for this file may be
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* found in 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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* Ported to ERC32 implementation of the SPARC by On-Line Applications
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* Research Corporation (OAR) under contract to the European Space
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* Agency (ESA).
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*
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* ERC32 modifications of respective RTEMS file: COPYRIGHT (c) 1995.
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* European Space Agency.
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*
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* $Id$
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*/
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#include <assert.h>
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#include <bsp.h>
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rtems_unsigned64 Timer_driver_Start_time;
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rtems_boolean Timer_driver_Find_average_overhead;
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static inline rtems_unsigned64 PPC_Get_timebase_register( void )
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{
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rtems_unsigned32 tbr_low;
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rtems_unsigned32 tbr_high;
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rtems_unsigned32 tbr_high_old;
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rtems_unsigned64 tbr;
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do {
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asm volatile( "mftbu %0" : "=r" (tbr_high_old));
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asm volatile( "mftb %0" : "=r" (tbr_low));
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asm volatile( "mftbu %0" : "=r" (tbr_high));
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} while ( tbr_high_old != tbr_high );
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tbr = tbr_high;
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tbr <<= 32;
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tbr |= tbr_low;
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return tbr;
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}
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void Timer_initialize()
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{
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/*
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* Timer runs long and accurate enough not to require an interrupt.
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*/
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Timer_driver_Start_time = PPC_Get_timebase_register();
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}
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#define AVG_OVERHEAD 24 /* It typically takes 24 instructions */
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/* to start/stop the timer. */
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#define LEAST_VALID 1 /* Don't trust a value lower than this */
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/* psim can count instructions. :) */
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int Read_timer()
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{
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rtems_unsigned64 clicks;
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rtems_unsigned64 total64;
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rtems_unsigned32 total;
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/* approximately CLOCK_SPEED clicks per microsecond */
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clicks = PPC_Get_timebase_register();
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assert( clicks > Timer_driver_Start_time );
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total64 = clicks - Timer_driver_Start_time;
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assert( total64 <= 0xffffffff ); /* fits into a unsigned32 */
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total = (rtems_unsigned32) total64;
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if ( Timer_driver_Find_average_overhead == 1 )
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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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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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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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