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/* timer.c
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*
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* This file manages the interval timer on the PowerPC MPC860.
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* NOTE: This is not the PIT, but rather the RTEMS interval
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* timer
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* We shall use the bottom 32 bits of the timebase register,
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*
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* The following was in the 403 version of this file. I don't
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* know what it means. JTM 5/19/98
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* NOTE: It is important that the timer start/stop overhead be
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* determined when porting or modifying this code.
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*
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* Author: Jay Monkman (jmonkman@frasca.com)
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* Copywright (C) 1998 by Frasca International, Inc.
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*
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* Derived from c/src/lib/libcpu/ppc/ppc403/timer/timer.c:
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*
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* Author: Andrew Bray <andy@i-cubed.co.uk>
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*
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* COPYRIGHT (c) 1995 by i-cubed ltd.
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*
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* To anyone who acknowledges that this file is provided "AS IS"
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* without any express or implied warranty:
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* permission to use, copy, modify, and distribute this file
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* for any purpose is hereby granted without fee, provided that
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* the above copyright notice and this notice appears in all
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* copies, and that the name of i-cubed limited not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* i-cubed limited makes no representations about the suitability
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* of this software for any purpose.
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*
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* Derived from c/src/lib/libcpu/hppa1_1/timer/timer.c:
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.OARcorp.com/rtems/license.html.
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*
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* $Id: timer.c,v 1.2 2001-09-27 12:01:29 chris Exp $
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*/
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#include <rtems.h>
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#include <mpc860.h>
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static volatile rtems_unsigned32 Timer_starting;
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static rtems_boolean Timer_driver_Find_average_overhead;
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/*
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* This is so small that this code will be reproduced where needed.
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*/
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static inline rtems_unsigned32 get_itimer(void)
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{
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rtems_unsigned32 ret;
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asm volatile ("mftb %0" : "=r" ((ret))); /* TBLO */
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return ret;
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}
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void Timer_initialize(void)
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{
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/* set interrupt level and enable timebase. This should never */
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/* generate an interrupt however. */
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m860.tbscr |= M860_TBSCR_TBIRQ(4) | M860_TBSCR_TBE;
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Timer_starting = get_itimer();
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}
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int Read_timer(void)
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{
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rtems_unsigned32 clicks;
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rtems_unsigned32 total;
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clicks = get_itimer();
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total = clicks - Timer_starting;
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if ( Timer_driver_Find_average_overhead == 1 )
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return total; /* in XXX microsecond units */
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else {
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if ( total < rtems_cpu_configuration_get_timer_least_valid() ) {
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return 0; /* below timer resolution */
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}
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return (total - rtems_cpu_configuration_get_timer_average_overhead());
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}
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}
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rtems_status_code Empty_function(void)
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{
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return RTEMS_SUCCESSFUL;
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}
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void Set_find_average_overhead(rtems_boolean find_flag)
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{
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Timer_driver_Find_average_overhead = find_flag;
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}
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