no_bsp/btimer/btimer.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /*  timer.c
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().  benchmark_timer_read() usually returns
0008  *  the number of microseconds since benchmark_timer_initialize() exitted.
0009  *
0010  *  NOTE: It is important that the timer start/stop overhead be
0011  *        determined when porting or modifying this code.
0012  *
0013  *  COPYRIGHT (c) 1989-1999.
0014  *  On-Line Applications Research Corporation (OAR).
0015  *
0016  * Redistribution and use in source and binary forms, with or without
0017  * modification, are permitted provided that the following conditions
0018  * are met:
0019  * 1. Redistributions of source code must retain the above copyright
0020  *    notice, this list of conditions and the following disclaimer.
0021  * 2. Redistributions in binary form must reproduce the above copyright
0022  *    notice, this list of conditions and the following disclaimer in the
0023  *    documentation and/or other materials provided with the distribution.
0024  *
0025  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0026  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0027  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0028  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0029  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0030  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0031  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0032  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0033  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0034  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0035  * POSSIBILITY OF SUCH DAMAGE.
0036  */
0037
0038 #include <rtems.h>
0039 #include <rtems/btimer.h>
0040 #include <bsp.h>
0041
0042 uint32_t         Timer_interrupts;
0043 bool benchmark_timer_find_average_overhead;
0044
0045 void benchmark_timer_initialize( void )
0046 {
0047
0048   /*
0049    *  Timer has never overflowed.  This may not be necessary on some
0050    *  implemenations of timer but ....
0051    */
0052
0053   Timer_interrupts = 0;
0054
0055   /*
0056    *  Somehow start the timer
0057    */
0058 }
0059
0060 /*
0061  *  The following controls the behavior of benchmark_timer_read().
0062  *
0063  *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
0064  *  is usually deducted from the number returned.
0065  *
0066  *  LEAST_VALID is the lowest number this routine should trust.  Numbers
0067  *  below this are "noise" and zero is returned.
0068  */
0069
0070 #define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
0071                              /* (Y countdowns) to start/stop the timer. */
0072                              /* This value is in microseconds. */
0073 #define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
0074
0075 benchmark_timer_t benchmark_timer_read( void )
0076 {
0077   uint32_t         clicks;
0078   uint32_t         total;
0079
0080   /*
0081    *  Read the timer and see how many clicks it has been since we started.
0082    */
0083
0084   clicks = 0;   /* XXX: read some HW here */
0085
0086   /*
0087    *  Total is calculated by taking into account the number of timer overflow
0088    *  interrupts since the timer was initialized and clicks since the last
0089    *  interrupts.
0090    */
0091
0092   total = clicks * 0;
0093
0094   if ( benchmark_timer_find_average_overhead == true )
0095     return total;          /* in XXX microsecond units */
0096   else {
0097     if ( total < LEAST_VALID )
0098       return 0;            /* below timer resolution */
0099   /*
0100    *  Somehow convert total into microseconds
0101    */
0102       return (total - AVG_OVERHEAD);
0103     }
0104 }
0105
0106 void benchmark_timer_disable_subtracting_average_overhead(
0107   bool find_flag
0108 )
0109 {
0110   benchmark_timer_find_average_overhead = find_flag;
0111 }