diff options
Diffstat (limited to 'c/src/lib/libbsp/arm/csb337/timer/timer.c')
-rw-r--r-- | c/src/lib/libbsp/arm/csb337/timer/timer.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/arm/csb337/timer/timer.c b/c/src/lib/libbsp/arm/csb337/timer/timer.c new file mode 100644 index 0000000000..c65dd8096a --- /dev/null +++ b/c/src/lib/libbsp/arm/csb337/timer/timer.c @@ -0,0 +1,91 @@ +/** + * @file + * @brief Cogent CSB337 Timer driver + * + * This uses timer 0 for timing measurments. + */ + +/* + * Copyright (c) 2004 by Jay Monkman <jtm@lopingdog.com> + * + * The license and distribution terms for this file may be + * found in the file LICENSE in this distribution or at + * http://www.rtems.org/license/LICENSE. + */ + +#include <bsp.h> +#include <rtems.h> +#include <rtems/btimer.h> +#include <at91rm9200.h> +#include <at91rm9200_pmc.h> + +uint16_t tstart; +bool benchmark_timer_find_average_overhead; +uint32_t tick_time; +/* + * Set up TC0 - + * timer_clock2 (MCK/8) + * capture mode - this shouldn't matter + */ +void benchmark_timer_initialize( void ) +{ + uint32_t tmr_freq; + + /* since we are using timer_clock2, divide mck by 8 */ + tmr_freq = at91rm9200_get_mck() / 8; + + TC_TC0_REG(TC_CMR) = TC_CMR_TCCLKS(1); /* timer_clock2 */ + TC_TC0_REG(TC_CCR) = (TC_CCR_CLKEN /* enable the counter */ + | TC_CCR_SWTRG); /* start it up */ + + /* tick time in nanoseconds */ + tick_time = 1000000000/tmr_freq; + +} + +/* + * The following controls the behavior of benchmark_timer_read(). + * + * AVG_OVEREHAD is the overhead for starting and stopping the timer. It + * is usually deducted from the number returned. + * + * LEAST_VALID is the lowest number this routine should trust. Numbers + * below this are "noise" and zero is returned. + */ + +#define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */ + /* (Y countdowns) to start/stop the timer. */ + /* This value is in microseconds. */ +#define LEAST_VALID 1 /* Don't trust a clicks value lower than this */ + +benchmark_timer_t benchmark_timer_read( void ) +{ + uint16_t t; + uint32_t total; + t = TC_TC0_REG(TC_CV); + + /* + * Total is calculated by taking into account the number of timer overflow + * interrupts since the timer was initialized and clicks since the last + * interrupts. + */ + + total = t * tick_time; + + if ( benchmark_timer_find_average_overhead == 1 ) + return total; /* in nanosecond units */ + else { + if ( total < LEAST_VALID ) + return 0; /* below timer resolution */ + /* + * Somehow convert total into microseconds + */ + return (total - AVG_OVERHEAD); + } +} + +void benchmark_timer_disable_subtracting_average_overhead(bool find_flag) +{ + benchmark_timer_find_average_overhead = find_flag; +} + |