[af85485] | 1 | /* |
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| 2 | * Cogent CSB337 Timer driver |
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| 3 | * |
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| 4 | * This uses timer 0 for timing measurments. |
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| 5 | * |
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| 6 | * Copyright (c) 2004 by Jay Monkman <jtm@lopingdog.com> |
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[359e537] | 7 | * |
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[af85485] | 8 | * The license and distribution terms for this file may be |
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| 9 | * found in the file LICENSE in this distribution or at |
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[c499856] | 10 | * http://www.rtems.org/license/LICENSE. |
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[af85485] | 11 | * |
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| 12 | * Notes: |
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| 13 | * This file manages the benchmark timer used by the RTEMS Timing Test |
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| 14 | * Suite. Each measured time period is demarcated by calls to |
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[18bfc42] | 15 | * benchmark_timer_initialize() and benchmark_timer_read(). benchmark_timer_read() usually returns |
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| 16 | * the number of microseconds since benchmark_timer_initialize() exitted. |
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[af85485] | 17 | * |
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[359e537] | 18 | * It is important that the timer start/stop overhead be determined |
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[af85485] | 19 | * when porting or modifying this code. |
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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 <at91rm9200.h> |
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| 25 | #include <at91rm9200_pmc.h> |
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| 26 | |
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[15ebe58b] | 27 | uint16_t tstart; |
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[3551166d] | 28 | bool benchmark_timer_find_average_overhead; |
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[15ebe58b] | 29 | uint32_t tick_time; |
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[af85485] | 30 | /* |
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[359e537] | 31 | * Set up TC0 - |
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[af85485] | 32 | * timer_clock2 (MCK/8) |
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| 33 | * capture mode - this shouldn't matter |
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| 34 | */ |
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[18bfc42] | 35 | void benchmark_timer_initialize( void ) |
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[af85485] | 36 | { |
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[15ebe58b] | 37 | uint32_t tmr_freq; |
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[af85485] | 38 | |
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| 39 | /* since we are using timer_clock2, divide mck by 8 */ |
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| 40 | tmr_freq = at91rm9200_get_mck() / 8; |
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| 41 | |
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| 42 | TC_TC0_REG(TC_CMR) = TC_CMR_TCCLKS(1); /* timer_clock2 */ |
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| 43 | TC_TC0_REG(TC_CCR) = (TC_CCR_CLKEN /* enable the counter */ |
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| 44 | | TC_CCR_SWTRG); /* start it up */ |
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| 45 | |
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| 46 | /* tick time in nanoseconds */ |
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| 47 | tick_time = 1000000000/tmr_freq; |
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| 48 | |
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| 49 | } |
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| 50 | |
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| 51 | /* |
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[18bfc42] | 52 | * The following controls the behavior of benchmark_timer_read(). |
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[af85485] | 53 | * |
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| 54 | * AVG_OVEREHAD is the overhead for starting and stopping the timer. It |
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| 55 | * is usually deducted from the number returned. |
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| 56 | * |
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| 57 | * LEAST_VALID is the lowest number this routine should trust. Numbers |
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| 58 | * below this are "noise" and zero is returned. |
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| 59 | */ |
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| 60 | |
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| 61 | #define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ |
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| 62 | /* (Y countdowns) to start/stop the timer. */ |
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| 63 | /* This value is in microseconds. */ |
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| 64 | #define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ |
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| 65 | |
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[18bfc42] | 66 | int benchmark_timer_read( void ) |
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[af85485] | 67 | { |
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[15ebe58b] | 68 | uint16_t t; |
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| 69 | uint32_t total; |
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[af85485] | 70 | t = TC_TC0_REG(TC_CV); |
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| 71 | |
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| 72 | /* |
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| 73 | * Total is calculated by taking into account the number of timer overflow |
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| 74 | * interrupts since the timer was initialized and clicks since the last |
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| 75 | * interrupts. |
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| 76 | */ |
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| 77 | |
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| 78 | total = t * tick_time; |
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| 79 | |
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[18bfc42] | 80 | if ( benchmark_timer_find_average_overhead == 1 ) |
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[af85485] | 81 | return total; /* in nanosecond units */ |
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| 82 | else { |
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| 83 | if ( total < LEAST_VALID ) |
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| 84 | return 0; /* below timer resolution */ |
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| 85 | /* |
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| 86 | * Somehow convert total into microseconds |
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| 87 | */ |
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| 88 | return (total - AVG_OVERHEAD); |
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| 89 | } |
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| 90 | } |
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| 91 | |
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[3551166d] | 92 | void benchmark_timer_disable_subtracting_average_overhead(bool find_flag) |
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[af85485] | 93 | { |
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[18bfc42] | 94 | benchmark_timer_find_average_overhead = find_flag; |
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[af85485] | 95 | } |
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| 96 | |
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