/* timer.c — ARM Generic Timer driver */

#include "timer.h"
#include "gic.h"

static volatile uint64_t ticks_count = 0;

void timer_init(void) {
    uint64_t freq = timer_get_freq();

    /* Set timer interval for 100Hz (freq/100 ticks per interrupt) */
    uint64_t interval = freq / 100;
    __asm__ volatile("msr cntp_tval_el0, %0" :: "r"(interval));

    /* Enable timer: unmask (bit 1=0), enable (bit 0=1) */
    __asm__ volatile("msr cntp_ctl_el0, %0" :: "r"(1UL));

    /* Enable timer IRQ on GIC */
    gic_enable_irq(IRQ_TIMER_CNTP);
}

void timer_irq(void) {
    ticks_count++;

    /* Acknowledge timer interrupt by writing new interval */
    uint64_t freq = timer_get_freq();
    __asm__ volatile("msr cntp_tval_el0, %0" :: "r"(freq / 100));
}

uint64_t timer_ticks(void) {
    return ticks_count;
}