banan-os/kernel/kernel/PIT.cpp

64 lines
1.3 KiB
C++

#include <kernel/IDT.h>
#include <kernel/InterruptController.h>
#include <kernel/IO.h>
#include <kernel/Scheduler.h>
#define TIMER0_CTL 0x40
#define TIMER1_CTL 0x41
#define TIMER2_CTL 0x42
#define PIT_CTL 0x43
#define SELECT_CHANNEL0 0x00
#define SELECT_CHANNEL1 0x40
#define SELECT_CHANNEL2 0x80
#define ACCESS_HI 0x10
#define ACCESS_LO 0x20
#define MODE_SQUARE_WAVE 0x06
#define BASE_FREQUENCY 1193182
#define TICKS_PER_SECOND 1000
namespace PIT
{
static volatile uint64_t s_system_time = 0;
void irq_handler()
{
s_system_time = s_system_time + 1;
Kernel::Scheduler::get().reschedule();
}
uint64_t ms_since_boot()
{
return s_system_time;
}
void initialize()
{
constexpr uint16_t timer_reload = BASE_FREQUENCY / TICKS_PER_SECOND;
IO::outb(PIT_CTL, SELECT_CHANNEL0 | ACCESS_LO | ACCESS_HI | MODE_SQUARE_WAVE);
IO::outb(TIMER0_CTL, (timer_reload >> 0) & 0xff);
IO::outb(TIMER0_CTL, (timer_reload >> 8) & 0xff);
IDT::register_irq_handler(PIT_IRQ, irq_handler);
InterruptController::get().enable_irq(PIT_IRQ);
}
void sleep(uint64_t ms)
{
if (ms == 0)
return;
uint64_t wake_time = s_system_time + ms;
Kernel::Scheduler::get().set_current_thread_sleeping(wake_time);
if (s_system_time < wake_time)
dwarnln("sleep woke {} ms too soon", wake_time - s_system_time);
}
}