1 | /* timer.c |
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2 | * |
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3 | * This file implements a benchmark timer using the General Purpose Timer on |
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4 | * the MEC. |
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5 | * |
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6 | * COPYRIGHT (c) 1989-1998. |
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7 | * On-Line Applications Research Corporation (OAR). |
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8 | * Copyright assigned to U.S. Government, 1994. |
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9 | * |
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10 | * The license and distribution terms for this file may be |
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11 | * found in found in the file LICENSE in this distribution or at |
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12 | * http://www.OARcorp.com/rtems/license.html. |
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13 | * |
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14 | * Ported to ERC32 implementation of the SPARC by On-Line Applications |
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15 | * Research Corporation (OAR) under contract to the European Space |
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16 | * Agency (ESA). |
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17 | * |
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18 | * ERC32 modifications of respective RTEMS file: COPYRIGHT (c) 1995. |
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19 | * European Space Agency. |
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20 | * |
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21 | * $Id$ |
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22 | */ |
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23 | |
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24 | #include <assert.h> |
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25 | |
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26 | #include <bsp.h> |
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27 | |
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28 | rtems_unsigned64 Timer_driver_Start_time; |
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29 | |
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30 | rtems_boolean Timer_driver_Find_average_overhead; |
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31 | |
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32 | static inline rtems_unsigned64 PPC_Get_timebase_register( void ) |
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33 | { |
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34 | rtems_unsigned32 tbr_low; |
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35 | rtems_unsigned32 tbr_high; |
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36 | rtems_unsigned32 tbr_high_old; |
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37 | rtems_unsigned64 tbr; |
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38 | |
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39 | do { |
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40 | asm volatile( "mftbu %0" : "=r" (tbr_high_old)); |
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41 | asm volatile( "mftb %0" : "=r" (tbr_low)); |
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42 | asm volatile( "mftbu %0" : "=r" (tbr_high)); |
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43 | } while ( tbr_high_old != tbr_high ); |
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44 | |
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45 | tbr = tbr_high; |
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46 | tbr <<= 32; |
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47 | tbr |= tbr_low; |
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48 | return tbr; |
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49 | } |
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50 | |
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51 | void Timer_initialize() |
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52 | { |
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53 | /* |
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54 | * Timer runs long and accurate enough not to require an interrupt. |
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55 | */ |
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56 | |
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57 | |
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58 | Timer_driver_Start_time = PPC_Get_timebase_register(); |
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59 | |
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60 | |
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61 | } |
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62 | |
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63 | #define AVG_OVERHEAD 24 /* It typically takes 24 instructions */ |
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64 | /* to start/stop the timer. */ |
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65 | #define LEAST_VALID 1 /* Don't trust a value lower than this */ |
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66 | /* psim can count instructions. :) */ |
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67 | |
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68 | int Read_timer() |
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69 | { |
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70 | rtems_unsigned64 clicks; |
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71 | rtems_unsigned64 total64; |
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72 | rtems_unsigned32 total; |
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73 | |
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74 | /* approximately CLOCK_SPEED clicks per microsecond */ |
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75 | |
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76 | clicks = PPC_Get_timebase_register(); |
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77 | |
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78 | assert( clicks > Timer_driver_Start_time ); |
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79 | |
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80 | total64 = clicks - Timer_driver_Start_time; |
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81 | |
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82 | assert( total64 <= 0xffffffff ); /* fits into a unsigned32 */ |
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83 | |
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84 | total = (rtems_unsigned32) total64; |
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85 | |
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86 | if ( Timer_driver_Find_average_overhead == 1 ) |
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87 | return total; /* in one microsecond units */ |
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88 | |
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89 | if ( total < LEAST_VALID ) |
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90 | return 0; /* below timer resolution */ |
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91 | |
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92 | return total - AVG_OVERHEAD; |
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93 | } |
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94 | |
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95 | rtems_status_code Empty_function( void ) |
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96 | { |
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97 | return RTEMS_SUCCESSFUL; |
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98 | } |
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99 | |
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100 | void Set_find_average_overhead( |
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101 | rtems_boolean find_flag |
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102 | ) |
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103 | { |
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104 | Timer_driver_Find_average_overhead = find_flag; |
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105 | } |
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