1 | /* timer.c |
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2 | * |
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3 | * This file manages the interval timer on the PowerPC MPC5xx. |
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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 | * |
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14 | * MPC5xx port sponsored by Defence Research and Development Canada - Suffield |
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15 | * Copyright (C) 2004, Real-Time Systems Inc. (querbach@realtime.bc.ca) |
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16 | * |
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17 | * Derived from c/src/lib/libcpu/powerpc/mpc8xx/timer/timer.c: |
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18 | * |
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19 | * Author: Jay Monkman (jmonkman@frasca.com) |
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20 | * Copywright (C) 1998 by Frasca International, Inc. |
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21 | * |
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22 | * Derived from c/src/lib/libcpu/ppc/ppc403/timer/timer.c: |
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23 | * |
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24 | * Author: Andrew Bray <andy@i-cubed.co.uk> |
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25 | * |
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26 | * COPYRIGHT (c) 1995 by i-cubed ltd. |
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27 | * |
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28 | * To anyone who acknowledges that this file is provided "AS IS" |
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29 | * without any express or implied warranty: |
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30 | * permission to use, copy, modify, and distribute this file |
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31 | * for any purpose is hereby granted without fee, provided that |
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32 | * the above copyright notice and this notice appears in all |
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33 | * copies, and that the name of i-cubed limited not be used in |
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34 | * advertising or publicity pertaining to distribution of the |
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35 | * software without specific, written prior permission. |
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36 | * i-cubed limited makes no representations about the suitability |
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37 | * of this software for any purpose. |
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38 | * |
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39 | * Derived from c/src/lib/libcpu/hppa1_1/timer/timer.c: |
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40 | * |
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41 | * COPYRIGHT (c) 1989-1998. |
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42 | * On-Line Applications Research Corporation (OAR). |
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43 | * |
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44 | * The license and distribution terms for this file may be |
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45 | * found in the file LICENSE in this distribution or at |
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46 | * http://www.rtems.com/license/LICENSE. |
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47 | * |
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48 | * $Id$ |
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49 | */ |
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50 | |
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51 | #include <rtems.h> |
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52 | #include <mpc5xx.h> |
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53 | |
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54 | static volatile rtems_unsigned32 Timer_starting; |
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55 | static rtems_boolean Timer_driver_Find_average_overhead; |
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56 | |
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57 | /* |
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58 | * This is so small that this code will be reproduced where needed. |
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59 | */ |
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60 | static inline rtems_unsigned32 get_itimer(void) |
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61 | { |
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62 | rtems_unsigned32 ret; |
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63 | |
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64 | asm volatile ("mftb %0" : "=r" ((ret))); /* TBLO */ |
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65 | |
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66 | return ret; |
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67 | } |
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68 | |
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69 | void Timer_initialize(void) |
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70 | { |
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71 | /* set interrupt level and enable timebase. This should never */ |
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72 | /* generate an interrupt however. */ |
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73 | usiu.tbscrk = USIU_UNLOCK_KEY; |
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74 | usiu.tbscr |= USIU_TBSCR_TBIRQ(4) /* interrupt priority level */ |
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75 | | USIU_TBSCR_TBF /* freeze timebase during debug */ |
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76 | | USIU_TBSCR_TBE; /* enable timebase */ |
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77 | usiu.tbscrk = 0; |
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78 | |
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79 | Timer_starting = get_itimer(); |
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80 | } |
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81 | |
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82 | #ifndef rtems_cpu_configuration_get_timer_least_valid |
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83 | #define rtems_cpu_configuration_get_timer_least_valid() 0 |
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84 | #endif |
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85 | |
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86 | #ifndef rtems_cpu_configuration_get_timer_average_overhead |
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87 | #define rtems_cpu_configuration_get_timer_average_overhead() 0 |
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88 | #endif |
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89 | |
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90 | int Read_timer(void) |
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91 | { |
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92 | rtems_unsigned32 clicks; |
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93 | rtems_unsigned32 total; |
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94 | |
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95 | clicks = get_itimer(); |
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96 | |
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97 | total = clicks - Timer_starting; |
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98 | |
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99 | if ( Timer_driver_Find_average_overhead == 1 ) |
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100 | return total; /* in XXX microsecond units */ |
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101 | |
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102 | else { |
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103 | if ( total < rtems_cpu_configuration_get_timer_least_valid() ) { |
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104 | return 0; /* below timer resolution */ |
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105 | } |
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106 | return (total - rtems_cpu_configuration_get_timer_average_overhead()); |
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107 | } |
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108 | } |
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109 | |
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110 | rtems_status_code Empty_function(void) |
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111 | { |
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112 | return RTEMS_SUCCESSFUL; |
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113 | } |
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114 | |
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115 | void Set_find_average_overhead(rtems_boolean find_flag) |
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116 | { |
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117 | Timer_driver_Find_average_overhead = find_flag; |
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118 | } |
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