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/* timer.c
*
* This file manages the interval timer on the PowerPC 403*.
* We shall use the bottom 32 bits of the timebase register,
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* Author: Andrew Bray <andy@i-cubed.co.uk>
*
* COPYRIGHT (c) 1995 by i-cubed ltd.
*
* To anyone who acknowledges that this file is provided "AS IS"
* without any express or implied warranty:
* permission to use, copy, modify, and distribute this file
* for any purpose is hereby granted without fee, provided that
* the above copyright notice and this notice appears in all
* copies, and that the name of i-cubed limited not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* i-cubed limited makes no representations about the suitability
* of this software for any purpose.
*
* Derived from c/src/lib/libcpu/hppa1_1/timer/timer.c:
*
* COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
* On-Line Applications Research Corporation (OAR).
* All rights assigned to U.S. Government, 1994.
*
* This material may be reproduced by or for the U.S. Government pursuant
* to the copyright license under the clause at DFARS 252.227-7013. This
* notice must appear in all copies of this file and its derivatives.
*
* $Id$
*/
#include <bsp.h>
#include <rtems.h>
extern rtems_cpu_table Cpu_table; /* owned by BSP */
static volatile rtems_unsigned32 Timer_starting;
static rtems_boolean Timer_driver_Find_average_overhead;
/*
* This is so small that this code will be reproduced where needed.
*/
static INLINE rtems_unsigned32 get_itimer(void)
{
rtems_unsigned32 ret;
asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); /* TBLO */
return ret;
}
void Timer_initialize()
{
rtems_unsigned32 iocr;
asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); /* IOCR */
iocr &= ~4;
iocr |= 4; /* Select external timer clock */
asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); /* IOCR */
Timer_starting = get_itimer();
}
int Read_timer()
{
rtems_unsigned32 clicks;
rtems_unsigned32 total;
clicks = get_itimer();
total = clicks - Timer_starting;
if ( Timer_driver_Find_average_overhead == 1 )
return total; /* in XXX microsecond units */
else {
if ( total < Cpu_table.timer_least_valid )
return 0; /* below timer resolution */
return (total - Cpu_table.timer_average_overhead);
}
}
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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