timer.c

Go to the documentation of this file.

 
#include <core/system.h>
#include <cpu/cpu.h>
#include <dev/irq.h>
#include <platform/virt.h>
 
static uint64_t freq, interval;
static void (*tick)(void);

static void timer_irq(void *arg __unused)
{
    /* the next tick comes `interval` counts from now */
    write_sysreg(cntv_tval_el0, interval);
 
    if (tick)
        tick();
}

uint64_t timer_setup(uint64_t period_ns, void (*handler)(void))
{
    freq = read_sysreg(cntfrq_el0);
    interval = freq * period_ns / 1000000000ULL;
    tick = handler;
 
    irq_install(VIRT_TIMER_IRQ, timer_irq, NULL);
 
    write_sysreg(cntv_tval_el0, interval);
    write_sysreg(cntv_ctl_el0, 1);      /* enabled, and not masked */
    isb();
 
    printk("timer: %ld Hz counter, the tick every %ld counts\n", freq, interval);
    return interval * 1000000000ULL / freq;
}
 
/*
 * Returns the monotonic clock: the counter's time since boot, in ns.
 */
uint64_t arch_rtime_ns(void)
{
    uint64_t f = read_sysreg(cntfrq_el0), c = read_sysreg(cntvct_el0);
    return c / f * 1000000000ULL + c % f * 1000000000ULL / f;
}
 
/*
 * Returns the time since boot, in microseconds.
 */
uint64_t arch_rtime_us(void)
{
    return arch_rtime_ns() / 1000;
}
 
/*
 * Returns the time since boot, in milliseconds.
 */
uint64_t arch_rtime_ms(void)
{
    return arch_rtime_ns() / 1000000;
}
 
/*
 * Returns the counter, which changes all the time, as a source of
 * randomness.
 */
uint64_t arch_cycles(void)
{
    return read_sysreg(cntvct_el0);
}