timer.h

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#ifndef __TIMER_H__
#define __TIMER_H__

#include "hvmm_types.h"
#include "arch_types.h"

/*
 * Implements Timer functionality such as,
 *
 * - timer channel: periodic callback at a given time interval
 * - current time: time since boot-up
 *
 * ==Example Usage==
 *
 * Initialize the timer module
 *  timer_init(timer_sched);
 *
 * Set interval 10 to timer_sched channel
 *  timer_set_interval( timer_sched, 10 );
 *
 * Set cb1 callback function to timer_scehd channel.
 * cb1 call after 10 interval.
 *  timer_set_callback( timer_sched, &cb1 );
 *
 * Start timer_sched channel. cb1 call after 10 interval.
 *  timer_start( timer_sched );
 */

#define TIMER_MAX_CHANNEL_CALLBACKS 8

typedef enum{
    timer_sched = 0,
    TIMER_NUM_MAX_CHANNELS
} timer_channel_t;

typedef void(*timer_callback_t)(void *pdata);

struct timer_channel{
    uint32_t interval_us;
    timer_callback_t callbacks[TIMER_MAX_CHANNEL_CALLBACKS];
};

/*
 * Calling this function is required only once in the entire system prior to calls 
 * to other functions of Timer module.
 */
hvmm_status_t timer_init(timer_channel_t channel);

/*
 * Starts the timer channel specified by 'channel'. The callback, 
 * if set, will be periodically called until it's unset or the channel stops by 
 * 'timer_stop(timer_channel)'
 */
hvmm_status_t timer_start(timer_channel_t channel);

/*
 *  Stops the timer channel specified by 'channel' 
 */
hvmm_status_t timer_stop(timer_channel_t channel);

/*
 * Sets time interval, in microseconds, for the timer channel. 
 * If the channel has been started and a callback function is set, it will be called 
 * in the next interval
 */
hvmm_status_t timer_set_interval(timer_channel_t channel, uint32_t interval_us);

/*
 * Returns the time interval for the timer channel if it was set previously. 
 * Unknown value is returned otherwise.
 */
uint32_t timer_get_interval(timer_channel_t channel);

/*
 * Adds a callback function for the timer channel.
 */
hvmm_status_t timer_add_callback(timer_channel_t channel, timer_callback_t handler);

/*
 * Removes the callback function from the timer channel's registered callback function list 
 * if it previously has been added.
 */
hvmm_status_t timer_remove_callback(timer_channel_t channel, timer_callback_t handler);

/* 
 * Converts from microseconds to system counter. 
 */
uint64_t timer_t2c(uint64_t time_us);
   
#endif