Timer Subsystem

Interface to the timer module in the MIPS r4300 processor. More...

Files
file	timer.c
	Timer Subsystem.
file	timer.h
	Timer Subsystem.

Data Structures
struct	timer_link_t
	Timer structure. More...
union	timer_link_t.__unnamed42__
	Callback function to call when timer fires. More...

Macros
#define	TF_ONE_SHOT   0
	Timer should fire only once.
#define	TF_CONTINUOUS   1
	Timer should fire at a regular interval.
#define	TF_DISABLED   2
	Timer is enabled or not. Can be used to get a new timer that's not started.
#define	TIMER_TICKS(us)   ((int)TIMER_TICKS_LL(us))
	Calculate timer ticks based on microseconds.
#define	TIMER_MICROS(tk)   ((int)TIMER_MICROS_LL(tk))
	Calculate microseconds based on timer ticks.
#define	TIMER_TICKS_LL(us)   ((long long)(us) * TICKS_PER_SECOND / 1000000)
	Calculate timer ticks based on microseconds.
#define	TIMER_MICROS_LL(tk)   ((long long)(tk) * 1000000 / TICKS_PER_SECOND)
	Calculate microseconds based on timer ticks.

Typedefs
typedef void(*	timer_callback1_t) (int ovfl)
	Timer callback function without context.
typedef void(*	timer_callback2_t) (int ovfl, void *ctx)
	Timer callback function with context.

Detailed Description

Interface to the timer module in the MIPS r4300 processor.

The timer subsystem allows code to receive a callback after a specified number of ticks or microseconds. It interfaces with the MIPS coprocessor 0 to handle the timer interrupt and provide useful timing services.

Before attempting to use the timer subsystem, code should call timer_init. After the timer subsystem has been initialized, a new one-shot or continuous timer can be created with new_timer. To remove an expired one-shot timer or a recurring timer, use delete_timer. To temporarily stop a timer, use stop_timer. To restart a stopped timer or an expired one-shot timer, use start_timer. Once code no longer needs the timer subsystem, a call to timer_close will free all continuous timers and shut down the timer subsystem. Note that timers removed with stop_timer or expired one-short timers will not be removed automatically and are the responsibility of the calling code to be freed, regardless of a call to timer_close.

Because the MIPS internal counter wraps around after ~90 seconds (see TICKS_READ), it's not possible to schedule a timer more than 90 seconds in the future.

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Data Structure Documentation

timer_link_t

struct timer_link_t

Timer structure.

Data Fields
uint32_t	left	Absolute ticks value at which the timer expires.
uint32_t	set	Ticks to set if continuous.
int	ovfl	To correct for drift.
int	flags	Timer flags. See TF_ONE_SHOT, TF_CONTINUOUS, and TF_DISABLED.
union timer_link_t.__unnamed42__	__unnamed__	Callback function to call when timer fires.
void *	ctx	Callback context parameter.
struct timer_link *	next	Link to next timer.

timer_link_t.__unnamed42__

union timer_link_t.__unnamed42__

Callback function to call when timer fires.

Data Fields
timer_callback1_t	callback
timer_callback2_t	callback_with_context

Macro Definition Documentation

TIMER_TICKS

#define TIMER_TICKS

(

us

)

((int)TIMER_TICKS_LL(us))

Calculate timer ticks based on microseconds.

Parameters

[in]

us

Microseconds to convert to ticks

Returns

Timer ticks

TIMER_MICROS

#define TIMER_MICROS

(

tk

)

((int)TIMER_MICROS_LL(tk))

Calculate microseconds based on timer ticks.

Parameters

[in]

tk

Ticks to convert to microseconds

Returns

Microseconds

TIMER_TICKS_LL

#define TIMER_TICKS_LL

(

us

)

((long long)(us) * TICKS_PER_SECOND / 1000000)

Calculate timer ticks based on microseconds.

Parameters

[in]

us

Microseconds to convert to ticks

Returns

Timer ticks as a long long

TIMER_MICROS_LL

#define TIMER_MICROS_LL

(

tk

)

((long long)(tk) * 1000000 / TICKS_PER_SECOND)

Calculate microseconds based on timer ticks.

Parameters

[in]

tk

Ticks to convert to microseconds

Returns

Microseconds as a long long