1 | /* timer.c |
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2 | * |
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3 | * This file manages the benchmark timer used by the RTEMS Timing Test |
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4 | * Suite. Each measured time period is demarcated by calls to |
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5 | * Timer_initialize() and Read_timer(). Read_timer() usually returns |
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6 | * the number of microseconds since Timer_initialize() exitted. |
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7 | * |
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8 | * This version returns the number of nanoseconds since Timer_initialize() |
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9 | * exited, since the '604 is very fast at 300MHz. Actual resolution is |
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10 | * 60 nsec. |
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11 | * |
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12 | * NOTE: It is important that the timer start/stop overhead be |
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13 | * determined when porting or modifying this code. |
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14 | * |
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15 | * COPYRIGHT (c) 1989-1999. |
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16 | * On-Line Applications Research Corporation (OAR). |
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17 | * |
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18 | * The license and distribution terms for this file may be |
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19 | * found in the file LICENSE in this distribution or at |
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20 | * http://www.OARcorp.com/rtems/license.html. |
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21 | * |
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22 | * $Id$ |
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23 | */ |
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24 | |
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25 | #include <rtems.h> |
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26 | #include <bsp.h> |
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27 | |
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28 | rtems_unsigned32 Timer_start; |
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29 | rtems_boolean Timer_driver_Find_average_overhead; |
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30 | |
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31 | void Timer_initialize( void ) |
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32 | { |
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33 | rtems_unsigned32 clicks; |
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34 | |
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35 | asm volatile ("mfspr %0,268" : "=r" (clicks) :); |
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36 | Timer_start = clicks; |
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37 | } |
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38 | |
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39 | /* |
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40 | * The following controls the behavior of Read_timer(). |
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41 | * |
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42 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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43 | * is usually deducted from the number returned. |
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44 | * |
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45 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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46 | * below this are "noise" and zero is returned. |
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47 | */ |
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48 | |
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49 | #define AVG_OVERHEAD 7 /* On average, it takes 7.4 nanoseconds */ |
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50 | /* (Y countdowns) to start/stop the timer. */ |
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51 | |
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52 | #define NSEC_PER_TICK 60 |
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53 | |
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54 | int Read_timer( void ) |
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55 | { |
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56 | rtems_unsigned32 clicks; |
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57 | rtems_unsigned32 total; |
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58 | |
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59 | /* |
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60 | * Read the timer and see how many clicks it has been since we started. |
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61 | * Timer overflows every 257 seconds, so multiple overflows are deemed |
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62 | * impossible. |
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63 | */ |
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64 | |
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65 | asm volatile ("mfspr %0,268" : "=r" (clicks) :); |
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66 | total = (clicks - Timer_start); |
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67 | |
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68 | if ( Timer_driver_Find_average_overhead == 1 ) { |
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69 | return total * NSEC_PER_TICK; /* in nanoseconds */ |
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70 | } else { |
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71 | /* |
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72 | * convert total into nanoseconds |
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73 | */ |
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74 | return total * NSEC_PER_TICK - AVG_OVERHEAD; |
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75 | } |
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76 | } |
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77 | |
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78 | /* |
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79 | * Empty function call used in loops to measure basic cost of looping |
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80 | * in Timing Test Suite. |
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81 | */ |
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82 | |
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83 | rtems_status_code Empty_function( void ) { |
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84 | return RTEMS_SUCCESSFUL; |
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85 | } |
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86 | |
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87 | void Set_find_average_overhead(rtems_boolean find_flag) { |
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88 | Timer_driver_Find_average_overhead = find_flag; |
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89 | } |
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90 | |
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