- cpu_disable_interrupt();
-
- // Setup APIC timer
-
- // Remap the IRQ 8 (rtc timer's vector) to RTC_TIMER_IV in ioapic
- // (Remarks IRQ 8 is pin INTIN8)
- // See IBM PC/AT Technical Reference 1-10 for old RTC IRQ
- // See Intel's Multiprocessor Specification for IRQ - IOAPIC INTIN
- // mapping config.
-
- // grab ourselves these irq numbers
- uint32_t iv_rtc = isrm_bindirq(PC_AT_IRQ_RTC, temp_intr_routine_rtc_tick);
- uint32_t iv_timer = isrm_ivexalloc(temp_intr_routine_apic_timer);
-
- // Setup a one-shot timer, we will use this to measure the bus speed. So we
- // can then calibrate apic timer to work at *nearly* accurate hz
- apic_write_reg(APIC_TIMER_LVT,
- LVT_ENTRY_TIMER(iv_timer, LVT_TIMER_ONESHOT));
-
- // Set divider to 64
- apic_write_reg(APIC_TIMER_DCR, APIC_TIMER_DIV64);
-
- /*
- Timer calibration process - measure the APIC timer base frequency
-
- step 1: setup a temporary isr for RTC timer which trigger at each tick
- (1024Hz)
- step 2: setup a temporary isr for #APIC_TIMER_IV
- step 3: setup the divider, APIC_TIMER_DCR
- step 4: Startup RTC timer
- step 5: Write a large value, v, to APIC_TIMER_ICR to start APIC timer
- (this must be followed immediately after step 4) step 6: issue a write to
- EOI and clean up.
-
- When the APIC ICR counting down to 0 #APIC_TIMER_IV triggered, save the
- rtc timer's counter, k, and disable RTC timer immediately (although the
- RTC interrupts should be blocked by local APIC as we are currently busy
- on handling #APIC_TIMER_IV)
-
- So the apic timer frequency F_apic in Hz can be calculate as
- v / F_apic = k / 1024
- => F_apic = v / k * 1024
-
- */
-
-#ifdef __LUNAIXOS_DEBUG__
- if (frequency < 1000) {
- kprintf(KWARN "Frequency too low. Millisecond timer might be dodgy.");
- }
-#endif
-
- timer_ctx->base_frequency = 0;
- rtc_counter = 0;
- apic_timer_done = 0;
-
- rtc_enable_timer(); // start RTC timer
- apic_write_reg(APIC_TIMER_ICR, APIC_CALIBRATION_CONST); // start APIC timer
-
- // enable interrupt, just for our RTC start ticking!
- cpu_enable_interrupt();
-
- wait_until(apic_timer_done);
-
- assert_msg(timer_ctx->base_frequency, "Fail to initialize timer (NOFREQ)");
-
- kprintf(KINFO "Base frequency: %u Hz\n", timer_ctx->base_frequency);