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#include <kernel/arch/amd64/acpi.h>
#include <kernel/arch/amd64/boot.h>
#include <kernel/arch/amd64/interrupts.h>
#include <kernel/panic.h>
#include <kernel/proc.h>
static Proc *scheduled = NULL;
static void *hpet = NULL;
static uint64_t hpet_period;
void hpet_init(void *base) {
if (hpet) panic_invalid_state();
hpet = base;
uint64_t *info = hpet;
uint64_t *cfg = hpet + 0x10;
hpet_period = *info >> 32;
*cfg |= 1<<0; /* enable */
}
uint64_t uptime_ns(void) {
if (hpet == NULL) panic_invalid_state();
uint64_t *counter = hpet + 0xF0;
unsigned __int128 femto = *counter * hpet_period;
uint64_t nano = femto / 1000000;
return nano;
}
static void pit_irq(void) {
Proc *p = scheduled;
if (p && p->waits4timer.goal < uptime_ns()) {
scheduled = p->waits4timer.next;
proc_setstate(p, PS_RUNNING);
}
}
void timer_schedule(Proc *p, uint64_t time) {
uint64_t now = uptime_ns();
/* to prevent leaking the current uptime, saturate instead of overflowing */
time = now + time;
if (time < now) {
time = ~0;
}
proc_setstate(p, PS_WAITS4TIMER);
p->waits4timer.goal = time;
Proc **slot = &scheduled;
while (*slot && (*slot)->waits4timer.goal <= time) {
assert((*slot)->state == PS_WAITS4TIMER);
slot = &(*slot)->waits4timer.next;
}
p->waits4timer.next = *slot;
*slot = p;
}
void timer_deschedule(Proc *p) {
assert(p->state == PS_WAITS4TIMER);
Proc **slot = &scheduled;
while (*slot && *slot != p)
slot = &(*slot)->waits4timer.next;
assert(*slot);
*slot = p->waits4timer.next;
proc_setstate(p, PS_RUNNING);
}
void timer_init(void) {
irq_fn[IRQ_PIT] = pit_irq;
}
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