1 | /* timer.c |
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2 | * |
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3 | * This file manages the benchmark timer used by the RTEMS Timing |
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4 | * Test Suite. Each measured time period is demarcated by calls to |
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5 | * benchmark_timer_initialize() and benchmark_timer_read(). |
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6 | * benchmark_timer_read() usually returns the number of microseconds |
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7 | * since benchmark_timer_initialize() exitted. |
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8 | * |
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9 | * NOTE: It is important that the timer start/stop overhead be |
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10 | * determined when porting or modifying this code. |
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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.com/license/LICENSE. |
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15 | * |
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16 | * $Id$ |
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17 | * |
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18 | * COPYRIGHT (c) Yann Sionneau <yann.sionneau@telecom-sudparis.eu> (GSoC 2010) |
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19 | * Telecom SudParis |
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20 | */ |
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21 | |
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22 | #include <rtems.h> |
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23 | #include <bsp.h> |
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24 | #include <rtems/btimer.h> |
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25 | #include "../include/system_conf.h" |
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26 | #include "../../shared/clock/clock.h" |
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27 | |
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28 | bool benchmark_timer_find_average_overhead; |
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29 | |
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30 | void benchmark_timer_initialize(void) |
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31 | { |
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32 | MM_WRITE(MM_TIMER1_COMPARE, 0xffffffff); |
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33 | MM_WRITE(MM_TIMER1_COUNTER, 0); |
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34 | MM_WRITE(MM_TIMER1_CONTROL, TIMER_ENABLE); |
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35 | } |
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36 | |
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37 | /* |
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38 | * The following controls the behavior of benchmark_timer_read(). |
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39 | * |
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40 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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41 | * is usually deducted from the number returned. |
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42 | * |
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43 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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44 | * below this are "noise" and zero is returned. |
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45 | */ |
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46 | |
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47 | #define AVG_OVERHEAD 4 /* It typically takes X.X microseconds */ |
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48 | /* (Y countdowns) to start/stop the timer. */ |
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49 | /* This value is in microseconds. */ |
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50 | #define LEAST_VALID 4 /* Don't trust a clicks value lower than this */ |
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51 | |
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52 | uint32_t benchmark_timer_read(void) |
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53 | { |
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54 | uint32_t ticks; |
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55 | uint32_t total; |
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56 | |
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57 | ticks = MM_READ(MM_TIMER1_COUNTER); |
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58 | if (ticks == 0xffffffff) |
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59 | printk("Timer overflow!\n"); |
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60 | |
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61 | total = ticks / (MM_READ(MM_FREQUENCY) / 1000000); |
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62 | |
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63 | if (benchmark_timer_find_average_overhead) |
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64 | return total; |
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65 | else |
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66 | { |
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67 | if (total < LEAST_VALID) |
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68 | return 0; |
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69 | |
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70 | return (total - AVG_OVERHEAD); |
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71 | } |
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72 | } |
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73 | |
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74 | void benchmark_timer_disable_subtracting_average_overhead( |
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75 | bool find_flag |
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76 | ) |
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77 | { |
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78 | benchmark_timer_find_average_overhead = find_flag; |
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79 | } |
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