Timecounter Support

The timecounter support provides directives to implement clock device drivers. More...

Files
file	timecounter.h
	This header file provides the Timecounter Support API.
file	tcsimpleinstall.c
	This source file contains the implementation of rtems_timecounter_simple_install().

Data Structures
struct	rtems_timecounter_simple
	Simple timecounter to support legacy clock drivers. More...

Macros
#define	RTEMS_TIMECOUNTER_QUALITY_CLOCK_DRIVER   100
	Timecounter quality for the clock drivers.

Typedefs
typedef void	rtems_timecounter_simple_at_tick(rtems_timecounter_simple *tc)
	At tick handling done under protection of the timecounter lock.
typedef uint32_t	rtems_timecounter_simple_get(rtems_timecounter_simple *tc)
	Returns the current value of a simple timecounter.
typedef bool	rtems_timecounter_simple_is_pending(rtems_timecounter_simple *tc)
	Returns true if the interrupt of a simple timecounter is pending, and false otherwise.

Functions
void	rtems_timecounter_simple_install (rtems_timecounter_simple *tc, uint32_t counter_frequency_in_hz, uint32_t counter_ticks_per_clock_tick, timecounter_get_t *get_timecount)
	Initializes and installs a simple timecounter.

Detailed Description

The timecounter support provides directives to implement clock device drivers.

Macro Definition Documentation

RTEMS_TIMECOUNTER_QUALITY_CLOCK_DRIVER

#define RTEMS_TIMECOUNTER_QUALITY_CLOCK_DRIVER   100

Timecounter quality for the clock drivers.

Timecounter with higher quality value are used in favour of those with lower quality value.

Function Documentation

rtems_timecounter_simple_install()

void rtems_timecounter_simple_install	(	rtems_timecounter_simple *	tc,
		uint32_t	counter_frequency_in_hz,
		uint32_t	counter_ticks_per_clock_tick,
		timecounter_get_t *	get_timecount
	)

Initializes and installs a simple timecounter.

A simple timecounter can be used if the hardware provides no free running counter. A periodic hardware counter must be provided. The counter period must be synchronous to the clock tick. The counter ticks per clock tick is scaled up to the next power of two.

Parameters

[in]	tc	Zero initialized simple timecounter.
[in]	counter_frequency_in_hz	The hardware counter frequency in Hz.
[in]	counter_ticks_per_clock_tick	The hardware counter ticks per clock tick.
[in]	get_timecount	The method to get the current time count.

#include <rtems/timecounter.h>
 
static rtems_timecounter_simple some_tc;
 
static uint32_t some_tc_get( rtems_timecounter_simple *tc )
{
  return some.value;
}
 
static bool some_tc_is_pending( rtems_timecounter_simple *tc )
{
  return some.is_pending;
}
 
static uint32_t some_tc_get_timecount( struct timecounter *tc )
{
  return rtems_timecounter_simple_downcounter_get(
    tc,
    some_tc_get,
    some_tc_is_pending
  );
}
 
static void some_tc_tick( void )
{
  rtems_timecounter_simple_downcounter_tick( &some_tc, some_tc_get );
}
 
void some_tc_init( void )
{
  uint64_t us_per_tick;
  uint32_t counter_frequency_in_hz;
  uint32_t counter_ticks_per_clock_tick;
 
  us_per_tick = rtems_configuration_get_microseconds_per_tick();
  counter_frequency_in_hz = some_tc_get_frequency();
  counter_ticks_per_clock_tick =
    (uint32_t) ( counter_frequency_in_hz * us_per_tick ) / 1000000;
 
  some_tc_init_hardware( counter_ticks_per_clock_tick );
  some_tc_init_clock_tick_interrupt( some_tc_tick );
 
  rtems_timecounter_simple_install(
    &some_tc,
    counter_frequency_in_hz,
    counter_ticks_per_clock_tick,
    some_tc_get_timecount
  );
}

See also

rtems_timecounter_simple_downcounter_get(), rtems_timecounter_simple_downcounter_tick(), rtems_timecounter_simple_upcounter_get() and rtems_timecounter_simple_upcounter_tick().