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/* timer.c
*
* This file manages the interval timer on the PowerPC MPC860.
* NOTE: This is not the PIT, but rather the RTEMS interval
* timer
* We shall use the bottom 32 bits of the timebase register,
*
* The following was in the 403 version of this file. I don't
* know what it means. JTM 5/19/98
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* Author: Jay Monkman (jmonkman@frasca.com)
* Copywright (C) 1998 by Frasca International, Inc.
*
* Derived from c/src/lib/libcpu/ppc/ppc403/timer/timer.c:
*
* 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) 1989-1998.
* On-Line Applications Research Corporation (OAR).
* Copyright assigned to U.S. Government, 1994.
*
* 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.
*
* $Id$
*/
#include <bsp.h>
#include <rtems.h>
#include <mpc860.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 ("mftb %0" : "=r" ((ret))); /* TBLO */
return ret;
}
void Timer_initialize(void)
{
/* set interrupt level and enable timebase. This should never */
/* generate an interrupt however. */
m860.tbscr |= M860_TBSCR_TBIRQ(4) | M860_TBSCR_TBE;
Timer_starting = get_itimer();
}
int Read_timer(void)
{
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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