1 | /* timer.c |
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2 | * |
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3 | * This file manages the interval timer on the PowerPC 403*. |
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4 | * We shall use the bottom 32 bits of the timebase register, |
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5 | * |
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6 | * NOTE: It is important that the timer start/stop overhead be |
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7 | * determined when porting or modifying this code. |
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8 | * |
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9 | * Author: Andrew Bray <andy@i-cubed.co.uk> |
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10 | * |
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11 | * COPYRIGHT (c) 1995 by i-cubed ltd. |
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12 | * |
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13 | * To anyone who acknowledges that this file is provided "AS IS" |
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14 | * without any express or implied warranty: |
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15 | * permission to use, copy, modify, and distribute this file |
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16 | * for any purpose is hereby granted without fee, provided that |
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17 | * the above copyright notice and this notice appears in all |
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18 | * copies, and that the name of i-cubed limited not be used in |
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19 | * advertising or publicity pertaining to distribution of the |
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20 | * software without specific, written prior permission. |
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21 | * i-cubed limited makes no representations about the suitability |
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22 | * of this software for any purpose. |
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23 | * |
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24 | * Derived from c/src/lib/libcpu/hppa1.1/timer/timer.c: |
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25 | * |
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26 | * COPYRIGHT (c) 1989-1999. |
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27 | * On-Line Applications Research Corporation (OAR). |
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28 | * |
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29 | * The license and distribution terms for this file may be |
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30 | * found in the file LICENSE in this distribution or at |
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31 | * http://www.OARcorp.com/rtems/license.html. |
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32 | * |
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33 | * Modifications for PPC405GP by Dennis Ehlin |
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34 | * |
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35 | * $Id$ |
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36 | * |
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37 | */ |
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38 | |
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39 | #include <rtems.h> |
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40 | |
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41 | static volatile rtems_unsigned32 Timer_starting; |
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42 | static rtems_boolean Timer_driver_Find_average_overhead; |
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43 | |
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44 | /* |
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45 | * This is so small that this code will be reproduced where needed. |
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46 | */ |
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47 | static inline rtems_unsigned32 get_itimer(void) |
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48 | { |
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49 | rtems_unsigned32 ret; |
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50 | |
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51 | #ifndef ppc405 |
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52 | asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); /* TBLO */ |
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53 | #else /* ppc405 */ |
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54 | /* asm volatile ("mfspr %0, 0x3dd" : "=r" ((ret))); TBLO */ |
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55 | |
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56 | asm volatile ("mfspr %0, 0x10c" : "=r" ((ret))); /* 405GP TBL */ |
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57 | #endif /* ppc405 */ |
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58 | |
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59 | return ret; |
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60 | } |
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61 | |
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62 | void Timer_initialize() |
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63 | { |
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64 | rtems_unsigned32 iocr; |
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65 | |
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66 | #ifndef ppc405 |
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67 | asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); /* IOCR */ |
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68 | iocr &= ~4; |
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69 | iocr |= 4; /* Select external timer clock */ |
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70 | asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); /* IOCR */ |
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71 | #else /* ppc405 */ |
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72 | asm volatile ("mfdcr %0, 0x0b2" : "=r" (iocr)); /*405GP CPC0_CR1 */ |
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73 | /* asm volatile ("mfdcr %0, 0xa0" : "=r" (iocr)); IOCR */ |
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74 | |
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75 | /* iocr |= 0x800000; select external timer clock CETE*/ |
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76 | iocr &= ~0x800000; /* timer clocked from system clock CETE*/ |
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77 | |
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78 | asm volatile ("mtdcr 0x0b2, %0" : "=r" (iocr) : "0" (iocr)); /* 405GP CPC0_CR1 */ |
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79 | /* asm volatile ("mtdcr 0xa0, %0" : "=r" (iocr) : "0" (iocr)); IOCR */ |
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80 | #endif /* ppc405 */ |
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81 | |
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82 | Timer_starting = get_itimer(); |
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83 | } |
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84 | |
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85 | int Read_timer() |
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86 | { |
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87 | rtems_unsigned32 clicks; |
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88 | rtems_unsigned32 total; |
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89 | |
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90 | clicks = get_itimer(); |
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91 | |
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92 | total = clicks - Timer_starting; |
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93 | |
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94 | if ( Timer_driver_Find_average_overhead == 1 ) |
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95 | return total; /* in XXX microsecond units */ |
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96 | |
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97 | else { |
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98 | if ( total < rtems_cpu_configuration_get_timer_least_valid() ) |
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99 | return 0; /* below timer resolution */ |
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100 | return (total - rtems_cpu_configuration_get_timer_average_overhead()); |
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101 | } |
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102 | } |
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103 | |
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104 | rtems_status_code Empty_function( void ) |
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105 | { |
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106 | return RTEMS_SUCCESSFUL; |
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107 | } |
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108 | |
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109 | void Set_find_average_overhead( |
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110 | rtems_boolean find_flag |
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111 | ) |
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112 | { |
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113 | Timer_driver_Find_average_overhead = find_flag; |
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114 | } |
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