[3084de2] | 1 | /* timer.c |
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| 2 | * |
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| 3 | * This file manages the interval timer on the PowerPC MPC821. |
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| 4 | * NOTE: This is not the PIT, but rather the RTEMS interval |
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| 5 | * timer |
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| 6 | * We shall use the bottom 32 bits of the timebase register, |
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| 7 | * |
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| 8 | * The following was in the 403 version of this file. I don't |
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| 9 | * know what it means. JTM 5/19/98 |
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| 10 | * NOTE: It is important that the timer start/stop overhead be |
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| 11 | * determined when porting or modifying this code. |
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| 12 | * |
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| 13 | * Author: Jay Monkman (jmonkman@frasca.com) |
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| 14 | * Copywright (C) 1998 by Frasca International, Inc. |
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| 15 | * |
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| 16 | * Derived from c/src/lib/libcpu/ppc/ppc403/timer/timer.c: |
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| 17 | * |
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| 18 | * Author: Andrew Bray <andy@i-cubed.co.uk> |
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| 19 | * |
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| 20 | * COPYRIGHT (c) 1995 by i-cubed ltd. |
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| 21 | * |
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| 22 | * To anyone who acknowledges that this file is provided "AS IS" |
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| 23 | * without any express or implied warranty: |
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| 24 | * permission to use, copy, modify, and distribute this file |
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| 25 | * for any purpose is hereby granted without fee, provided that |
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| 26 | * the above copyright notice and this notice appears in all |
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| 27 | * copies, and that the name of i-cubed limited not be used in |
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| 28 | * advertising or publicity pertaining to distribution of the |
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| 29 | * software without specific, written prior permission. |
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| 30 | * i-cubed limited makes no representations about the suitability |
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| 31 | * of this software for any purpose. |
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| 32 | * |
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| 33 | * Derived from c/src/lib/libcpu/hppa1_1/timer/timer.c: |
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| 34 | * |
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| 35 | * COPYRIGHT (c) 1989-1998. |
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| 36 | * On-Line Applications Research Corporation (OAR). |
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| 37 | * Copyright assigned to U.S. Government, 1994. |
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| 38 | * |
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| 39 | * The license and distribution terms for this file may be |
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| 40 | * found in the file LICENSE in this distribution or at |
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| 41 | * http://www.OARcorp.com/rtems/license.html. |
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| 42 | * |
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| 43 | * $Id$ |
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| 44 | */ |
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| 45 | |
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| 46 | #include <bsp.h> |
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| 47 | #include <rtems.h> |
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| 48 | #include <mpc821.h> |
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| 49 | |
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| 50 | extern rtems_cpu_table Cpu_table; /* owned by BSP */ |
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| 51 | |
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| 52 | static volatile rtems_unsigned32 Timer_starting; |
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| 53 | static rtems_boolean Timer_driver_Find_average_overhead; |
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| 54 | |
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| 55 | /* |
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| 56 | * This is so small that this code will be reproduced where needed. |
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| 57 | */ |
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| 58 | static inline rtems_unsigned32 get_itimer(void) |
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| 59 | { |
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| 60 | rtems_unsigned32 ret; |
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| 61 | |
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| 62 | asm volatile ("mftb %0" : "=r" ((ret))); /* TBLO */ |
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| 63 | |
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| 64 | return ret; |
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| 65 | } |
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| 66 | |
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| 67 | void Timer_initialize(void) |
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| 68 | { |
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| 69 | /* set interrupt level and enable timebase. This should never */ |
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| 70 | /* generate an interrupt however. */ |
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| 71 | m821.tbscr |= M821_TBSCR_TBIRQ(4) | M821_TBSCR_TBE; |
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| 72 | |
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| 73 | Timer_starting = get_itimer(); |
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| 74 | } |
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| 75 | |
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| 76 | int Read_timer(void) |
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| 77 | { |
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| 78 | rtems_unsigned32 clicks; |
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| 79 | rtems_unsigned32 total; |
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| 80 | |
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| 81 | clicks = get_itimer(); |
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| 82 | |
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| 83 | total = clicks - Timer_starting; |
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| 84 | |
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| 85 | if ( Timer_driver_Find_average_overhead == 1 ) |
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| 86 | return total; /* in XXX microsecond units */ |
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| 87 | |
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| 88 | else { |
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| 89 | if ( total < Cpu_table.timer_least_valid ) { |
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| 90 | return 0; /* below timer resolution */ |
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| 91 | } |
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| 92 | return (total - Cpu_table.timer_average_overhead); |
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| 93 | } |
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| 94 | } |
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| 95 | |
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| 96 | rtems_status_code Empty_function(void) |
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| 97 | { |
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| 98 | return RTEMS_SUCCESSFUL; |
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| 99 | } |
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| 100 | |
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| 101 | void Set_find_average_overhead(rtems_boolean find_flag) |
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| 102 | { |
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| 103 | Timer_driver_Find_average_overhead = find_flag; |
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| 104 | } |
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