shared/dev/timer.c

0001 /**
0002  *  @file
0003  *  @brief Timer for Blackfin
0004  *
0005  *  This file manages the benchmark timer used by the RTEMS Timing Test
0006  *  Suite.  Each measured time period is demarcated by calls to
0007  *  benchmark_timer_initialize() and benchmark_timer_read().
0008  *  benchmark_timer_read() usually returns the number of microseconds
0009  *  since benchmark_timer_initialize() exitted.
0010  */
0011
0012 /*
0013  *  Copyright (c) 2006 by Atos Automacao Industrial Ltda.
0014  *             written by Alain Schaefer <alain.schaefer@easc.ch>
0015  *                    and Antonio Giovanini <antonio@atos.com.br>
0016  *
0017  *  The license and distribution terms for this file may be
0018  *  found in the file LICENSE in this distribution or at
0019  *  http://www.rtems.org/license/LICENSE.
0020  */
0021
0022 #include <rtems.h>
0023 #include <bsp.h>
0024 #include <rtems/btimer.h>
0025
0026 uint32_t  Timer_interrupts;
0027 bool      benchmark_timer_find_average_overhead;
0028
0029 /*
0030  * benchmark_timer_initialize
0031  *
0032  * Blackfin processor has a counter for clock cycles.
0033  */
0034 void benchmark_timer_initialize( void )
0035 {
0036
0037   /*reset counters*/
0038   __asm__ ("R2 = 0;");
0039   __asm__ ("CYCLES = R2;");
0040   __asm__ ("CYCLES2 = R2;");
0041   /*start counters*/
0042   __asm__ ("R2 = SYSCFG;");
0043   __asm__ ("BITSET(R2,1);");
0044   __asm__ ("SYSCFG = R2");
0045
0046 }
0047
0048 /*
0049  *  The following controls the behavior of benchmark_timer_read().
0050  *
0051  *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
0052  *  is usually deducted from the number returned.
0053  *
0054  *  LEAST_VALID is the lowest number this routine should trust.  Numbers
0055  *  below this are "noise" and zero is returned.
0056  */
0057
0058 #define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
0059                              /* (Y countdowns) to start/stop the timer. */
0060                              /* This value is in microseconds. */
0061 #define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
0062
0063 benchmark_timer_t benchmark_timer_read( void )
0064 {
0065   uint32_t          clicks;
0066   uint32_t          total;
0067   register uint32_t cycles __asm__ ("R2");
0068
0069   /* stop counter */
0070   __asm__ ("R2 = SYSCFG;");
0071   __asm__ ("BITCLR(R2,1);");
0072   __asm__ ("SYSCFG = R2;");
0073   __asm__ ("R2 = CYCLES;");
0074
0075
0076   clicks = cycles; /* Clock cycles */
0077
0078   /* converting to microseconds */
0079   total = clicks / (CCLK/1000000);
0080
0081   if ( benchmark_timer_find_average_overhead == 1 )
0082     return total;          /* in XXX microsecond units */
0083   else {
0084     if ( total < LEAST_VALID )
0085       return 0;            /* below timer resolution */
0086   /*
0087    *  Somehow convert total into microseconds
0088    */
0089       return (total - AVG_OVERHEAD);
0090     }
0091 }
0092
0093 void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
0094 {
0095   benchmark_timer_find_average_overhead = find_flag;
0096 }