jmr3904/btimer/btimer.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /*
0004  *  This file implements a benchmark timer using a TX39 timer.
0005  *
0006  *  NOTE: On the simulator, the count directly reflects instructions.
0007  *
0008  *  COPYRIGHT (c) 1989-2000.
0009  *  On-Line Applications Research Corporation (OAR).
0010  *
0011  * Redistribution and use in source and binary forms, with or without
0012  * modification, are permitted provided that the following conditions
0013  * are met:
0014  * 1. Redistributions of source code must retain the above copyright
0015  *    notice, this list of conditions and the following disclaimer.
0016  * 2. Redistributions in binary form must reproduce the above copyright
0017  *    notice, this list of conditions and the following disclaimer in the
0018  *    documentation and/or other materials provided with the distribution.
0019  *
0020  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0021  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0022  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0023  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0024  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0025  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0026  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0027  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0028  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0029  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0030  * POSSIBILITY OF SUCH DAMAGE.
0031  */
0032
0033 #include <assert.h>
0034
0035 #include <bsp.h>
0036 #include <rtems/btimer.h>
0037
0038 bool benchmark_timer_find_average_overhead;
0039
0040 void benchmark_timer_initialize(void)
0041 {
0042   /*
0043    *  Programming the compare register as the maximum value should let
0044    *  it run long enough and accurate enough not to require an interrupt.
0045    *  but if it ever does generate an interrupt, we will simply fault.
0046    *
0047    *  NOTE:  This is similar to the clock driver initialization
0048    *         with the exception that the divider is disabled and
0049    *         the compare register is set to the maximum value.
0050    */
0051
0052   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_TCR,   0x20 );
0053   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_CCDR, 0x3 );
0054   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_TRR, 0x0 );
0055   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_CPRA, 0xFFFFFFFF );
0056   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_TISR, 0x00 );
0057   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_ITMR, 0x0001 );
0058   TX3904_TIMER_WRITE( TX3904_TIMER1_BASE, TX3904_TIMER_TCR,   0xe0 );
0059 }
0060
0061 #define AVG_OVERHEAD      0  /* It typically takes N instructions */
0062                              /*     to start/stop the timer. */
0063 #define LEAST_VALID       1  /* Don't trust a value lower than this */
0064                              /* tx39 simulator can count instructions. :) */
0065
0066 benchmark_timer_t benchmark_timer_read(void)
0067 {
0068   uint32_t          total;
0069
0070   total = TX3904_TIMER_READ( TX3904_TIMER1_BASE, TX3904_TIMER_TRR );
0071
0072   if ( benchmark_timer_find_average_overhead == true )
0073     return total;          /* in one microsecond units */
0074
0075   if ( total < LEAST_VALID )
0076     return 0;            /* below timer resolution */
0077
0078   return total - AVG_OVERHEAD;
0079 }
0080
0081 void benchmark_timer_disable_subtracting_average_overhead(
0082   bool find_flag
0083 )
0084 {
0085   benchmark_timer_find_average_overhead = find_flag;
0086 }