Module timer 

Timer Implementation

Provides timer functionality for the kernel:

• PIT (Programmable Interval Timer) for legacy fallback
• APIC Timer for modern systems (calibrated via PIT channel 2)

Constants

NS_PER_TICK

Nanoseconds per timer tick (derived from TIMER_HZ).

PIT_CHANNEL0_PORT 🔒

Programmable Interval Timer (PIT) constants

PIT_COMMAND_PORT 🔒

PIT_FREQUENCY 🔒

TIMER_HZ

Kernel timer frequency in Hz.

Statics

APIC_TICKS_PER_10MS 🔒

Cached APIC ticks per 10ms from calibration (used by APs)

APIC_TIMER_ACTIVE 🔒

Whether the APIC timer is currently active

Functions

apic_ticks_per_10ms

Return the cached calibration value (ticks per 10ms).

calibrate_apic_timer

Calibrate the APIC timer using PIT channel 2 as a reference.

init_pit

Initialize the Programmable Interval Timer (PIT)

is_apic_timer_active

Check if the APIC timer is active

start_apic_timer

Start the APIC timer in periodic mode.

start_apic_timer_cached

Start the APIC timer using the cached calibration value.

stop_pit

Stop PIT channel 0 to prevent phantom interrupts.