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/*
* Cogent CSB336 Timer driver
*
* This uses timer 2 for timing measurments.
*
* Copyright (c) 2004 Cogent Computer Systems
* Written by Jay Monkman <jtm@lopingdog.com>
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
*
* http://www.rtems.com/license/LICENSE.
*
* Notes:
* This file manages the benchmark timer used by the RTEMS Timing Test
* Suite. Each measured time period is demarcated by calls to
* benchmark_timerinitialize() and benchmark_timerread(). benchmark_timerread() usually returns
* the number of microseconds since benchmark_timerinitialize() exitted.
*
* It is important that the timer start/stop overhead be determined
* when porting or modifying this code.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
#include <mc9328mxl.h>
uint32_t g_start;
uint32_t g_freq;
rtems_boolean benchmark_timerfind_average_overhead;
/*
* Set up Timer 1
*/
void benchmark_timerinitialize( void )
{
MC9328MXL_TMR2_TCTL = (MC9328MXL_TMR_TCTL_CLKSRC_PCLK1 |
MC9328MXL_TMR_TCTL_FRR |
MC9328MXL_TMR_TCTL_TEN);
/* set prescaler to 1 (register value + 1) */ \
MC9328MXL_TMR2_TPRER = 0;
/* get freq of counter in KHz */
g_freq = get_perclk1_freq() / 1000;
g_start = MC9328MXL_TMR2_TCN;
}
/*
* The following controls the behavior of benchmark_timerread().
*
* 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.
*/
#define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */
/* (Y countdowns) to start/stop the timer. */
/* This value is in microseconds. */
#define LEAST_VALID 1 /* Don't trust a clicks value lower than this */
int benchmark_timerread( void )
{
uint32_t t;
unsigned long long total;
t = MC9328MXL_TMR2_TCN;
/*
* Total is calculated by taking into account the number of timer overflow
* interrupts since the timer was initialized and clicks since the last
* interrupts.
*/
total = (t - g_start);
/* convert to nanoseconds */
total = (total * 1000)/ g_freq;
if ( benchmark_timerfind_average_overhead == 1 ) {
return (int) total;
} else if ( total < LEAST_VALID ) {
return 0;
}
/*
* Somehow convert total into microseconds
*/
return (total - AVG_OVERHEAD);
}
/*
* Empty function call used in loops to measure basic cost of looping
* in Timing Test Suite.
*/
rtems_status_code benchmark_timerempty_function( void )
{
return RTEMS_SUCCESSFUL;
}
void benchmark_timerdisable_subtracting_average_overhead(
rtems_boolean find_flag
)
{
benchmark_timerfind_average_overhead = find_flag;
}
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