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/*
* timer driver for the Hitachi SH 7750
*
* 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.
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* Copyright (C) 2001 OKTET Ltd., St.-Petersburg, Russia
* Author: Victor V. Vengerov <vvv@oktet.ru>
*
* COPYRIGHT (c) 1998.
* On-Line Applications Research Corporation (OAR).
*
* 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.
*
* $Id$
*/
#include <rtems.h>
#include <rtems/score/sh_io.h>
#include <rtems/score/iosh7750.h>
#ifndef TIMER_PRIO
#define TIMER_PRIO 15
#endif
/* Timer prescaler division ratio */
#define TIMER_PRESCALER 4
#define TCR1_TPSC SH7750_TCR_TPSC_DIV4
#define TIMER_VECTOR SH7750_EVT_TO_NUM(SH7750_EVT_TUNI1)
rtems_isr timerisr();
static uint32_t Timer_interrupts;
/* Counter should be divided to this value to obtain time in microseconds */
static uint32_t microseconds_divider;
/* Interrupt period in microseconds */
static uint32_t microseconds_per_int;
rtems_boolean Timer_driver_Find_average_overhead;
/* Timer_initialize --
* Initialize Timer 1 to operate as a RTEMS benchmark timer:
* - determine timer clock frequency
* - install timer interrupt handler
* - configure the Timer 1 hardware
* - start the timer
*
* PARAMETERS:
* none
*
* RETURNS:
* none
*/
void
Timer_initialize(void)
{
uint8_t temp8;
uint16_t temp16;
rtems_interrupt_level level;
rtems_isr *ignored;
int cpudiv = 1;
int tidiv = 1;
Timer_interrupts = 0;
_CPU_ISR_Disable(level);
/* Get CPU frequency divider from clock unit */
switch (read16(SH7750_FRQCR) & SH7750_FRQCR_IFC)
{
case SH7750_FRQCR_IFCDIV1:
cpudiv = 1;
break;
case SH7750_FRQCR_IFCDIV2:
cpudiv = 2;
break;
case SH7750_FRQCR_IFCDIV3:
cpudiv = 3;
break;
case SH7750_FRQCR_IFCDIV4:
cpudiv = 4;
break;
case SH7750_FRQCR_IFCDIV6:
cpudiv = 6;
break;
case SH7750_FRQCR_IFCDIV8:
cpudiv = 8;
break;
default:
rtems_fatal_error_occurred( RTEMS_NOT_CONFIGURED);
}
/* Get peripheral module frequency divider from clock unit */
switch (read16(SH7750_FRQCR) & SH7750_FRQCR_PFC)
{
case SH7750_FRQCR_PFCDIV2:
tidiv = 2 * TIMER_PRESCALER;
break;
case SH7750_FRQCR_PFCDIV3:
tidiv = 3 * TIMER_PRESCALER;
break;
case SH7750_FRQCR_PFCDIV4:
tidiv = 4 * TIMER_PRESCALER;
break;
case SH7750_FRQCR_PFCDIV6:
tidiv = 6 * TIMER_PRESCALER;
break;
case SH7750_FRQCR_PFCDIV8:
tidiv = 8 * TIMER_PRESCALER;
break;
default:
rtems_fatal_error_occurred( RTEMS_NOT_CONFIGURED);
}
microseconds_divider =
rtems_cpu_configuration_get_clicks_per_second() * cpudiv /
(tidiv * 1000000);
microseconds_per_int = 0xFFFFFFFF / microseconds_divider;
/*
* Hardware specific initialization
*/
/* Stop the Timer 0 */
temp8 = read8(SH7750_TSTR);
temp8 &= ~SH7750_TSTR_STR1;
write8(temp8, SH7750_TSTR);
/* Establish interrupt handler */
_CPU_ISR_install_raw_handler( TIMER_VECTOR, timerisr, &ignored );
/* Reset timer constant and counter */
write32(0xFFFFFFFF, SH7750_TCOR1);
write32(0xFFFFFFFF, SH7750_TCNT1);
/* Select timer mode */
write16(
SH7750_TCR_UNIE | /* Enable Underflow Interrupt */
SH7750_TCR_CKEG_RAISE | /* Count on rising edge */
TCR1_TPSC, /* Timer prescaler ratio */
SH7750_TCR1);
/* Set timer interrupt priority */
temp16 = read16(SH7750_IPRA);
temp16 = (temp16 & ~SH7750_IPRA_TMU1) | (TIMER_PRIO << SH7750_IPRA_TMU1_S);
write16(temp16, SH7750_IPRA);
_CPU_ISR_Enable(level);
/* Start the Timer 1 */
temp8 = read8(SH7750_TSTR);
temp8 |= SH7750_TSTR_STR1;
write8(temp8, SH7750_TSTR);
}
/*
* The following controls the behavior of Read_timer().
*
* AVG_OVERHEAD 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 0 /* 20 */ /* Don't trust a clicks value lower than this */
/* Read_timer --
* Read timer value in microsecond units since timer start.
*
* PARAMETERS:
* none
*
* RETURNS:
* number of microseconds since timer has been started
*/
int
Read_timer(void)
{
uint32_t clicks;
uint32_t ints;
uint32_t total ;
rtems_interrupt_level level;
uint32_t tcr;
_CPU_ISR_Disable(level);
clicks = 0xFFFFFFFF - read32(SH7750_TCNT1);
tcr = read32(SH7750_TCR1);
ints = Timer_interrupts;
_CPU_ISR_Enable(level);
/* Handle the case when timer overflowed but interrupt was not processed */
if ((clicks > 0xFF000000) && ((tcr & SH7750_TCR_UNF) != 0))
{
ints++;
}
total = microseconds_per_int * ints + (clicks / microseconds_divider);
if ( Timer_driver_Find_average_overhead )
return total; /* in microsecond units */
else
{
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
/*
* Somehow convert total into microseconds
*/
return (total - AVG_OVERHEAD) ;
}
}
/* Empty_function --
* Empty function call used in loops to measure basic cost of looping
* in Timing Test Suite.
*
* PARAMETERS:
* none
*
* RETURNS:
* RTEMS_SUCCESSFUL
*/
rtems_status_code
Empty_function( void )
{
return RTEMS_SUCCESSFUL;
}
/* Set_find_average_overhead --
* This routine is invoked by the "Check Timer" (tmck) test in the
* RTEMS Timing Test Suite. It makes the Read_timer routine not
* subtract the overhead required to initialize and read the benchmark
* timer.
*
* PARAMETERS:
* find_flag - boolean flag, TRUE if overhead must not be subtracted.
*
* RETURNS:
* none
*/
void
Set_find_average_overhead(rtems_boolean find_flag)
{
Timer_driver_Find_average_overhead = find_flag;
}
/* timerisr --
* Timer interrupt handler routine. This function invoked on timer
* underflow event; once per 2^32 clocks. It should reset the timer
* event and increment timer interrupts counter.
*/
void
timerisr(void)
{
uint8_t temp8;
/* reset the flags of the status register */
temp8 = read8(SH7750_TCR1) & ~SH7750_TCR_UNF;
write8(temp8, SH7750_TCR1);
Timer_interrupts += 1;
}
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