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/*
* S3C2400 Timer driver
*
* This uses timer 1 for timing measurments.
*
* 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_timer_initialize() and benchmark_timer_read(). benchmark_timer_read() usually returns
* the number of microseconds since benchmark_timer_initialize() 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 <s3c24xx.h>
uint32_t g_start;
uint32_t g_freq;
bool benchmark_timer_find_average_overhead;
/*
* Set up Timer 1
*/
void benchmark_timer_initialize( void )
{
uint32_t cr;
/* stop TIMER1*/
cr=rTCON & 0xFFFFF0FF;
rTCON=(cr | (0x0 << 8));
/* set MUX for Timer1 to 1/2 */
cr=rTCFG1 & 0xFFFFFF0F;
rTCFG1=(cr | (0<<4));
/* input freq=PLCK/2 Mhz*/
g_freq = get_PCLK() / 2000;
rTCNTB1 = 0xFFFF;
/* start TIMER1 with manual reload */
cr=rTCON & 0xFFFFF0FF;
rTCON=(cr | (0x1 << 9));
rTCON=(cr | (0x1 << 8));
g_start = rTCNTO1;
}
/*
* The following controls the behavior of benchmark_timer_read().
*
* 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_timer_read( void )
{
uint32_t t;
unsigned long long total;
t = rTCNTO1;
/*
* 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 = (g_start - t);
/* convert to microseconds */
total = (total*1000) / g_freq;
if ( benchmark_timer_find_average_overhead == 1 ) {
return (int) total;
} else if ( total < LEAST_VALID ) {
return 0;
}
/*
* Somehow convert total into microseconds
*/
return (total - AVG_OVERHEAD);
}
void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
{
benchmark_timer_find_average_overhead = find_flag;
}
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