feat: acpi, apic, apic timer

src/arch/x86_64/timer.rs

@@ -0,0 +1,82 @@
+use core::sync::atomic::{AtomicBool, AtomicU32, Ordering};
+
+use crate::{
+    arch::{
+        apic::{self, LocalApic},
+        disable_interrupts,
+        io_apic::IoApic,
+        x86_64::{
+            interrupts::enable_interrupts,
+            pit::{PIT_CALIBRATION_COUNT, PIT_FREQUENCY, Pit},
+        },
+    },
+    platform::acpi::IsaIrqRoute,
+};
+
+static PIT_FIRED: AtomicBool = AtomicBool::new(false);
+static LAPIC_COUNT_AT_PIT: AtomicU32 = AtomicU32::new(0);
+
+#[derive(Debug)]
+pub enum TimerCalibrationError {
+    PitTimeout,
+    IoApicNotHandled,
+    FrequencyOverflow,
+    InvalidTimerCount,
+}
+
+pub fn calibrate_local_apic(
+    local_apic: &mut LocalApic,
+    io_apic: &mut IoApic,
+    pit_route: IsaIrqRoute,
+) -> Result<u64, TimerCalibrationError> {
+    PIT_FIRED.store(false, Ordering::SeqCst);
+    LAPIC_COUNT_AT_PIT.store(0, Ordering::SeqCst);
+
+    io_apic
+        .unmask(pit_route.gsi)
+        .map_err(|_| TimerCalibrationError::IoApicNotHandled)?;
+    local_apic.start_calibration_counter();
+
+    Pit::start_one_shot(PIT_CALIBRATION_COUNT);
+
+    enable_interrupts();
+
+    while !PIT_FIRED.load(Ordering::SeqCst) {
+        if apic::current_timer_count() == 0 {
+            disable_interrupts();
+            let _ = io_apic.mask(pit_route.gsi);
+            local_apic.stop_timer();
+
+            return Err(TimerCalibrationError::PitTimeout);
+        }
+
+        core::hint::spin_loop();
+    }
+
+    disable_interrupts();
+
+    io_apic
+        .mask(pit_route.gsi)
+        .map_err(|_| TimerCalibrationError::IoApicNotHandled)?;
+    local_apic.stop_timer();
+
+    let elapsed = u32::MAX - LAPIC_COUNT_AT_PIT.load(Ordering::SeqCst);
+
+    if elapsed == 0 {
+        return Err(TimerCalibrationError::InvalidTimerCount);
+    }
+
+    let ticks_per_second = (elapsed as u64)
+        .checked_mul(PIT_FREQUENCY)
+        .ok_or(TimerCalibrationError::FrequencyOverflow)?
+        / PIT_CALIBRATION_COUNT as u64;
+
+    Ok(ticks_per_second)
+}
+
+pub fn record_pit_calibration() {
+    let current = apic::current_timer_count();
+
+    LAPIC_COUNT_AT_PIT.store(current, Ordering::SeqCst);
+    PIT_FIRED.store(true, Ordering::SeqCst);
+}