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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.OARcorp.com/rtems/license.html.
*
* Notes:
* This file manages the benchmark timer used by the RTEMS Timing Test
* Suite. Each measured time period is demarcated by calls to
* Timer_initialize() and Read_timer(). Read_timer() usually returns
* the number of microseconds since 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 <s3c2400.h>
uint32_t g_start;
uint32_t g_freq;
rtems_boolean Timer_driver_Find_average_overhead;
/*
* Set up Timer 1
*/
void Timer_initialize( void )
{
uint32_t cr;
uint32_t m;
uint32_t p;
uint32_t s;
/* stop TIMER1*/
cr=rTCON & 0xFFFFF0FF;
rTCON=(cr | (0x0 << 8));
/* set MUX for Timer1 to 1/2 */
cr=rTCFG1 & 0xFFFFFF0F;
rTCFG1=(cr | (0<<4));
/* compute MPLL freq */
m = M_MDIV + 8;
p = M_PDIV + 2;
s = M_SDIV;
g_freq =(BSP_OSC_FREQ * m) / (p << s);
/* PCLK = MPLL/4 */
g_freq = g_freq / 4;
/* input freq=PLCK/2 Mhz*/
g_freq = g_freq / 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 Read_timer().
*
* 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 Read_timer( 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 ( Timer_driver_Find_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 Empty_function( void )
{
return RTEMS_SUCCESSFUL;
}
void Set_find_average_overhead(
rtems_boolean find_flag
)
{
Timer_driver_Find_average_overhead = find_flag;
}
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