1 | /** |
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2 | * @file |
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3 | * @brief Cogent CSB336 Timer driver |
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4 | * |
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5 | * This uses timer 2 for timing measurments. |
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6 | */ |
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7 | |
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8 | /* |
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9 | * Copyright (c) 2004 Cogent Computer Systems |
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10 | * Written by Jay Monkman <jtm@lopingdog.com> |
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11 | * |
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12 | * The license and distribution terms for this file may be |
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13 | * found in the file LICENSE in this distribution or at |
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14 | * http://www.rtems.org/license/LICENSE. |
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15 | */ |
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16 | |
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17 | #include <rtems.h> |
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18 | #include <bsp.h> |
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19 | #include <rtems/btimer.h> |
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20 | #include <mc9328mxl.h> |
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21 | |
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22 | uint32_t g_start; |
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23 | uint32_t g_freq; |
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24 | |
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25 | bool benchmark_timer_find_average_overhead; |
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26 | |
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27 | |
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28 | /* |
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29 | * Set up Timer 1 |
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30 | */ |
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31 | void benchmark_timer_initialize( void ) |
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32 | { |
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33 | MC9328MXL_TMR2_TCTL = (MC9328MXL_TMR_TCTL_CLKSRC_PCLK1 | |
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34 | MC9328MXL_TMR_TCTL_FRR | |
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35 | MC9328MXL_TMR_TCTL_TEN); |
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36 | /* set prescaler to 1 (register value + 1) */ \ |
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37 | MC9328MXL_TMR2_TPRER = 0; |
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38 | |
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39 | /* get freq of counter in KHz */ |
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40 | g_freq = get_perclk1_freq() / 1000; |
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41 | |
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42 | g_start = MC9328MXL_TMR2_TCN; |
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43 | } |
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44 | |
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45 | /* |
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46 | * The following controls the behavior of benchmark_timer_read(). |
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47 | * |
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48 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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49 | * is usually deducted from the number returned. |
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50 | * |
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51 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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52 | * below this are "noise" and zero is returned. |
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53 | */ |
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54 | |
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55 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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56 | /* (Y countdowns) to start/stop the timer. */ |
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57 | /* This value is in microseconds. */ |
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58 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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59 | |
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60 | benchmark_timer_t benchmark_timer_read( void ) |
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61 | { |
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62 | uint32_t t; |
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63 | unsigned long long total; |
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64 | |
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65 | t = MC9328MXL_TMR2_TCN; |
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66 | /* |
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67 | * Total is calculated by taking into account the number of timer overflow |
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68 | * interrupts since the timer was initialized and clicks since the last |
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69 | * interrupts. |
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70 | */ |
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71 | |
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72 | total = (t - g_start); |
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73 | |
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74 | /* convert to nanoseconds */ |
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75 | total = (total * 1000)/ g_freq; |
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76 | |
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77 | if ( benchmark_timer_find_average_overhead == 1 ) { |
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78 | return (int) total; |
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79 | } else if ( total < LEAST_VALID ) { |
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80 | return 0; |
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81 | } |
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82 | /* |
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83 | * Somehow convert total into microseconds |
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84 | */ |
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85 | |
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86 | return (total - AVG_OVERHEAD); |
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87 | } |
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88 | |
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89 | void benchmark_timer_disable_subtracting_average_overhead(bool find_flag) |
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90 | { |
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91 | benchmark_timer_find_average_overhead = find_flag; |
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92 | } |
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93 | |
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