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Diffstat (limited to 'c/src/lib/libbsp/arm/edb7312/timer/timer.c')
-rw-r--r-- | c/src/lib/libbsp/arm/edb7312/timer/timer.c | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/arm/edb7312/timer/timer.c b/c/src/lib/libbsp/arm/edb7312/timer/timer.c new file mode 100644 index 0000000000..954a35f86c --- /dev/null +++ b/c/src/lib/libbsp/arm/edb7312/timer/timer.c @@ -0,0 +1,93 @@ +/* + * Cirrus EP7312 Timer driver + * + * Copyright (c) 2002 by Jay Monkman <jtm@smoothsmoothie.com> + * + * The license and distribution terms for this file may be + * found in the file LICENSE in this distribution or at + * + * http://www.OARcorp.com/rtems/license.html. + * + * Notes: + * This file manages the benchmark timer used by the RTEMS Timing Test + * Suite. Each measured time period is demarcated by calls to + * Timer_initialize() and Read_timer(). Read_timer() usually returns + * the number of microseconds since Timer_initialize() exitted. + * + * It is important that the timer start/stop overhead be determined + * when porting or modifying this code. + * + * $Id$ +*/ + +#include <rtems.h> +#include <bsp.h> +#include <ep7312.h> + +rtems_unsigned16 tstart; +rtems_boolean Timer_driver_Find_average_overhead; + +void Timer_initialize( void ) +{ + *EP7312_SYSCON1 |= EP7312_SYSCON1_TC2_512KHZ; + *EP7312_TC2D = 0xffff; +} + +/* + * The following controls the behavior of Read_timer(). + * + * 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 */ + +int Read_timer( void ) +{ + rtems_unsigned16 t; + rtems_unsigned32 total; + t = *EP7312_TC2D; + + /* + * 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 = (unsigned32)0x0000ffff - t; /* result is 1/512000 = ~2 uS */ + total = (total * 1953) / 1000; /* convert to uS */ + if ( Timer_driver_Find_average_overhead == 1 ) + return total; /* in XXX microsecond units */ + else { + if ( total < LEAST_VALID ) + return 0; /* below timer resolution */ + /* + * Somehow convert total into microseconds + */ + return (total - AVG_OVERHEAD); + } +} + +/* + * Empty function call used in loops to measure basic cost of looping + * in Timing Test Suite. + */ + +rtems_status_code Empty_function( void ) +{ + return RTEMS_SUCCESSFUL; +} + +void Set_find_average_overhead( + rtems_boolean find_flag +) +{ + Timer_driver_Find_average_overhead = find_flag; +} + |