#include "lib.h"

#define TMU_CHANNEL 2

#define BASE_TICKS_PER_US 200

#define CLOCK_DIVIDER 16

#define TOCR 0xFFD80000  /* Output control register */

#define TSTR 0xFFD80004  /* Start register */

#define TCOR(c) (0xFFD80008 + (c*12))  /* Constant register */

#define TCNT(c) (0xFFD8000C + (c*12))  /* Count register */

#define TCR(c)  (0xFFD80010 + (c*12))  /* Control register */

/**

 * Initialize the on-chip timer controller. We snag TMU channel 2 in its

 * highest resolution mode, and start it counting down from max_int. 

 */

void timer_init() {

    unsigned int val = byte_read(TSTR);

    byte_write( TSTR, val & (~(1<<TMU_CHANNEL)) ); /* Stop counter */

    long_write( TCOR(TMU_CHANNEL), 0xFFFFFFFF );

    long_write( TCNT(TMU_CHANNEL), 0xFFFFFFFF );

    word_write( TCR(TMU_CHANNEL), 0x00000000 );

}

void timer_run() {

    byte_write( TSTR, byte_read(TSTR) | (1<<TMU_CHANNEL) );

}

void timer_start() {

    timer_init();

    timer_run();

}

/**

 * Report the current value of TMU2.

 */

unsigned int timer_gettime() {

    return long_read(TCNT(TMU_CHANNEL));

}

/**

 * Stop TMU2 and report the current value.

 */

unsigned int timer_stop() {

    long_write( TSTR, long_read(TSTR) & (~(1<<TMU_CHANNEL)) );

    return long_read( TCNT(TMU_CHANNEL) );

}

/**

 * Convert the supplied timer value to a number of micro seconds since the timer

 * was started.

 */

unsigned int timer_to_microsecs( unsigned int value ) {

    return (0xFFFFFFFF - value) * CLOCK_DIVIDER / BASE_TICKS_PER_US;

}

unsigned int timer_gettime_us() {

    return timer_to_microsecs( timer_gettime() );

}