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) 1989-1999. |
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7 | * On-Line Applications Research Corporation (OAR). |
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8 | * |
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9 | * The license and distribution terms for this file may be |
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10 | * found in the file LICENSE in this distribution or at |
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11 | * http://www.rtems.com/license/LICENSE. |
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12 | * |
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13 | * Ported to ERC32 implementation of the SPARC by On-Line Applications |
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14 | * Research Corporation (OAR) under contract to the European Space |
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15 | * Agency (ESA). |
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16 | * |
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17 | * ERC32 modifications of respective RTEMS file: COPYRIGHT (c) 1995. |
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18 | * European Space Agency. |
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19 | * |
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20 | * $Id$ |
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21 | */ |
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22 | |
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23 | |
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24 | #include <bsp.h> |
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25 | |
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26 | rtems_boolean Timer_driver_Find_average_overhead; |
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27 | |
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28 | rtems_boolean Timer_driver_Is_initialized = FALSE; |
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29 | |
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30 | void Timer_initialize() |
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31 | { |
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32 | /* |
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33 | * Timer runs long and accurate enough not to require an interrupt. |
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34 | */ |
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35 | |
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36 | if ( Timer_driver_Is_initialized == FALSE ) { |
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37 | |
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38 | /* approximately 1 us per countdown */ |
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39 | ERC32_MEC.General_Purpose_Timer_Scalar = CLOCK_SPEED - 1; |
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40 | ERC32_MEC.General_Purpose_Timer_Counter = 0xffffffff; |
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41 | |
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42 | } else { |
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43 | Timer_driver_Is_initialized = TRUE; |
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44 | } |
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45 | |
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46 | ERC32_MEC_Set_General_Purpose_Timer_Control( |
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47 | ERC32_MEC_TIMER_COUNTER_ENABLE_COUNTING | |
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48 | ERC32_MEC_TIMER_COUNTER_LOAD_COUNTER |
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49 | ); |
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50 | |
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51 | ERC32_MEC_Set_General_Purpose_Timer_Control( |
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52 | ERC32_MEC_TIMER_COUNTER_ENABLE_COUNTING |
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53 | ); |
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54 | |
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55 | } |
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56 | |
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57 | #define AVG_OVERHEAD 3 /* It typically takes 3.0 microseconds */ |
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58 | /* to start/stop the timer. */ |
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59 | #define LEAST_VALID 2 /* Don't trust a value lower than this */ |
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60 | |
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61 | int Read_timer() |
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62 | { |
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63 | uint32_t total; |
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64 | |
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65 | total = ERC32_MEC.General_Purpose_Timer_Counter; |
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66 | |
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67 | total = 0xffffffff - total; |
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68 | |
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69 | if ( Timer_driver_Find_average_overhead == 1 ) |
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70 | return total; /* in one microsecond units */ |
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71 | |
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72 | if ( total < LEAST_VALID ) |
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73 | return 0; /* below timer resolution */ |
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74 | |
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75 | return total - AVG_OVERHEAD; |
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76 | } |
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77 | |
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78 | rtems_status_code Empty_function( void ) |
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79 | { |
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80 | return RTEMS_SUCCESSFUL; |
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81 | } |
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82 | |
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83 | void Set_find_average_overhead( |
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84 | rtems_boolean find_flag |
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85 | ) |
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86 | { |
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87 | Timer_driver_Find_average_overhead = find_flag; |
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88 | } |
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