Timer functions
[RTAI schedulers modules]


Files

file  sched_up.c
 Scheduling function for uni-processor.


Functions

void rt_set_periodic_mode (void)
 Set timer mode.

void rt_set_oneshot_mode (void)
 Set timer mode.

RTIME start_rt_timer (int period)
 Start timer.

void start_rt_apic_timers (struct apic_timer_setup_data *setup_mode, unsigned int rcvr_jiffies_cpuid)
 Start local apic timer.

void stop_rt_timer (void)
 Stop timer.

RTIME count2nano (RTIME counts)
 Convert internal count units to nanoseconds.

RTIME nano2count (RTIME ns)
 Convert nanoseconds to internal count units.

RTIME count2nano_cpuid (RTIME counts, unsigned int cpuid)
 Convert internal count units to nanoseconds.

RTIME nano2count_cpuid (RTIME ns, unsigned int cpuid)
 Convert nanoseconds to internal count units.

RTIME rt_get_time (void)
 Get the current time.

RTIME rt_get_time_cpuid (unsigned int cpuid)
 Get the current time.

RTIME rt_get_time_ns (void)
 Get the current time.

RTIME rt_get_time_ns_cpuid (unsigned int cpuid)
 Get the current time.

RTIME rt_get_cpu_time_ns (void)
 Get the current time.


Function Documentation

RTIME count2nano RTIME  counts  ) 
 

Convert internal count units to nanoseconds.

This function converts the time of timercounts internal count units into nanoseconds. Remember that the count units are related to the time base being used (see functions rt_set_oneshot_mode() and rt_set_periodic_mode() for an explanation).

Parameters:
counts internal count units.
Returns:
The given time in nanoseconds is returned.

RTIME count2nano_cpuid RTIME  counts,
unsigned int  cpuid
 

Convert internal count units to nanoseconds.

This function converts the time of timercounts internal count units into nanoseconds. It is to be used with the MUP scheduler since with such a scheduler it is possible to have independent timers, i.e. periodic of different periods or a mixing of periodic and oneshot, so that it is impossible to establish which conversion units should be used in the case one asks for a conversion from any CPU for any other CPU. All these functions have the same behavior with UP and SMP schedulers.

Parameters:
counts internal count units.
cpuid Identifier of the CPU (FIXME).
Returns:
The given time in nanoseconds is returned.

RTIME nano2count RTIME  ns  ) 
 

Convert nanoseconds to internal count units.

This function converts the time of nanosecs nanoseconds into internal counts units. Remember that the count units are related to the time base being used (see functions rt_set_oneshot_mode() and rt_set_periodic_mode() for an explanation).

The versions ending with_cpuid are to be used with the MUP scheduler since with such a scheduler it is possible to have independent timers, i.e. periodic of different periods or a mixing of periodic and oneshot, so that it is impossible to establish which conversion units should be used in the case one asks for a conversion from any CPU for any other CPU. All these functions have the same behavior with UP and SMP schedulers.

Parameters:
ns Number of nanoseconds.
Returns:
The given time in nanoseconds is returned.

RTIME nano2count_cpuid RTIME  ns,
unsigned int  cpuid
 

Convert nanoseconds to internal count units.

This function converts the time of nanosecs nanoseconds into internal counts units. Remember that the count units are related to the time base being used (see functions rt_set_oneshot_mode() and rt_set_periodic_mode() for an explanation).

This function is to be used with the MUP scheduler since with such a scheduler it is possible to have independent timers, i.e. periodic of different periods or a mixing of periodic and oneshot, so that it is impossible to establish which conversion units should be used in the case one asks for a conversion from any CPU for any other CPU. All these functions have the same behavior with UP and SMP schedulers.

Parameters:
ns Number of nanoseconds.
cpuid Identifier of the CPU (FIXME).
Returns:
The given time in nanoseconds is returned.

RTIME rt_get_cpu_time_ns void   ) 
 

Get the current time.

rt_get_cpu_time_ns always returns the CPU time in nanoseconds whatever timer is in use.

Returns:
The current time in internal count units is returned.

RTIME rt_get_time void   ) 
 

Get the current time.

rt_get_time returns the time, in internal count units, since start_rt_timer was called. In periodic mode this number is in multiples of the periodic tick. In oneshot mode it is directly the TSC count for CPUs having a time stamp clock (TSC), while it is a (FIXME) on 8254 units for those not having it (see functions rt_set_oneshot_mode() and rt_set_periodic_mode() for an explanation).

Returns:
The current time in internal count units is returned.

RTIME rt_get_time_cpuid unsigned int  cpuid  ) 
 

Get the current time.

rt_get_time_cpuid returns the time, in internal count units, since start_rt_timer was called. In periodic mode this number is in multiples of the periodic tick. In oneshot mode it is directly the TSC count for CPUs having a time stamp clock (TSC), while it is a (FIXME) on 8254 units for those not having it (see functions rt_set_oneshot_mode() and rt_set_periodic_mode() for an explanation). This version ending with _cpuid must be used with the MUP scheduler when there is the need to declare from which cpuid the time must be gotten (FIXME). In fact one can need to get the time of another CPU and timers can differ from CPU to CPU. (FIXME) All these functions have the same behavior with UP and SMP schedulers.

Parameters:
cpuid corresponds to the CPUI identifier.
Returns:
The current time in internal count units is returned.

RTIME rt_get_time_ns void   ) 
 

Get the current time.

rt_get_time_ns is the same as rt_get_time() but the returned time is converted to nanoseconds.

Returns:
The current time in internal count units is returned.

RTIME rt_get_time_ns_cpuid unsigned int  cpuid  ) 
 

Get the current time.

rt_get_time_ns is the same as rt_get_time but the returned time is converted to nanoseconds. The version ending with _cpuid must be used with the MUP scheduler when there is the need to declare from which cpuidthe time must be got. In fact one can need to get the time of another CPU and timers can differ from CPU to CPU. All these functions have the same behavior with UP and SMP schedulers.

Parameters:
cpuid corresponds to the CPUI identifier.
Returns:
The current time in internal count units is returned.

void rt_set_oneshot_mode void   ) 
 

Set timer mode.

rt_set_periodic_mode sets the periodic mode for the timer. It consists of a fixed frequency timing of the tasks in multiple of the period set with a call to start_rt_timer(). The resolution is that of the 8254 (1193180 Hz) on a UP machine, or if the 8254 based SMP scheduler is being used. For the SMP scheduler timed by the local APIC timer and for the MUP scheduler the timer resolution is that of the local APIC timer frequency, generally the bus frequency divided 16. Any timing request not being an integer multiple of the set timer period is satisfied at the closest period tick. It is the default mode when no call is made to set the oneshot mode.

Note:
Stopping the timer by stop_rt_timer() sets the timer back into its default (periodic) mode. Always call rt_set_oneshot_mode() before each start_rt_timer() if you want to be sure to have it oneshot on multiple insmod without rmmoding the RTAI scheduler in use.

void rt_set_periodic_mode void   ) 
 

Set timer mode.

rt_set_periodic_mode sets the periodic mode for the timer. It consists of a fixed frequency timing of the tasks in multiple of the period set with a call to start_rt_timer(). The resolution is that of the 8254 (1193180 Hz) on a UP machine, or if the 8254 based SMP scheduler is being used. For the SMP scheduler timed by the local APIC timer and for the MUP scheduler the timer resolution is that of the local APIC timer frequency, generally the bus frequency divided 16. Any timing request not being an integer multiple of the set timer period is satisfied at the closest period tick. It is the default mode when no call is made to set the oneshot mode.

Note:
Stopping the timer by stop_rt_timer() sets the timer back into its default (periodic) mode. Always call rt_set_oneshot_mode() before each start_rt_timer() if you want to be sure to have it oneshot on multiple insmod without rmmoding the RTAI scheduler in use.

void start_rt_apic_timers struct apic_timer_setup_data *  setup_mode,
unsigned int  rcvr_jiffies_cpuid
 

Start local apic timer.

start_rt_apic_timers starts local APIC timers according to what is found in setup_data.

Parameters:
setup_mode is a pointer to an array of structures apic_timer_setup_data, see function rt_setup_apic_timers (FIXME) in RTAI module functions described further on in this manual.
rcvr_jiffies_cpuid is the CPU number whose time log has to be used to keep Linux timing and pacing in tune. This function is specific to the MUP scheduler. If it is called with either the UP or SMP scheduler it will use:
  • a periodic timer if all local APIC timers are periodic with the same period;
  • a oneshot timer if all the local APIC timers are oneshot, or have different timing modes, are periodic with different periods.

RTIME start_rt_timer int  period  ) 
 

Start timer.

start_rt_timer starts the timer with a period period. The period is in internal count units and is required only for the periodic mode. In the oneshot mode the period value is ignored. This functions uses the 8254 with the UP and the 8254 based SMP scheduler. Otherwise it uses a single local APIC with the APIC based SMP schedulers and an APIC for each CPU with the MUP scheduler. In the latter case all local APIC timers are paced in the same way, according to the timer mode set.

Returns:
The period in internal count units.

void stop_rt_timer void   ) 
 

Stop timer.

stop_rt_timer stops the timer. The timer mode is set to periodic.

Returns:
The period in internal count units.


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