From e480bd0ed068bcbfc09be9a8688045c3bd2cbd94 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Wed, 25 Oct 2023 12:02:44 -0400
Subject: [PATCH] Enable PIT ISR to count milliseconds

---
 src/hulk/apic.d | 10 ++++++++++
 src/hulk/hulk.d |  3 ++-
 src/hulk/pit.d  |  8 ++++++--
 src/hulk/rtc.d  |  2 --
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/hulk/apic.d b/src/hulk/apic.d
index e388d84..2fa25e0 100644
--- a/src/hulk/apic.d
+++ b/src/hulk/apic.d
@@ -7,11 +7,14 @@ import hulk.hurl;
 import hulk.acpi;
 import hulk.idt;
 import hulk.rtc;
+import hulk.pit;
+import hulk.klog;
 
 struct Apic
 {
     private enum uint PERIODIC_MODE = 0x2_0000u;
 
+    private enum ulong IRQ_PIT = 2u;
     private enum ulong IRQ_RTC = 8u;
 
     static struct ApicRegister
@@ -77,6 +80,8 @@ struct Apic
         apic_registers.lvt_timer.value = Idt.INT_APIC_TIMER;
         apic_registers.lvt_lint[0].value = Idt.INT_APIC_LINT0;
         apic_registers.lvt_lint[1].value = Idt.INT_APIC_LINT1;
+        /* Enable PIT interrupt. */
+        configure_io_apic_irq(IRQ_PIT, Idt.INT_APIC_BASE + IRQ_PIT);
         /* Enable RTC interrupt. */
         configure_io_apic_irq(IRQ_RTC, Idt.INT_APIC_BASE + IRQ_RTC);
     }
@@ -99,11 +104,16 @@ struct Apic
     {
         switch (vector)
         {
+        case Idt.INT_APIC_BASE + IRQ_PIT:
+            Pit.isr();
+            break;
+
         case Idt.INT_APIC_BASE + IRQ_RTC:
             Rtc.isr();
             break;
 
         default:
+            Klog.writefln("Unhandled APIC ISR %u", vector);
             break;
         }
         eoi();
diff --git a/src/hulk/hulk.d b/src/hulk/hulk.d
index 59e94fe..d20a80f 100644
--- a/src/hulk/hulk.d
+++ b/src/hulk/hulk.d
@@ -23,6 +23,7 @@ import hulk.apic;
 import hulk.rtc;
 import hulk.serial;
 import hulk.usb;
+import hulk.pit;
 
 extern extern(C) __gshared ubyte _hulk_bss_size;
 
@@ -81,7 +82,7 @@ void hulk_start()
     Rtc.time t = Rtc.read_rtc_time();
     Klog.writefln("System time is 20%02u-%02u-%02u %02u:%02u:%02u",
             t.year, t.month, t.day, t.hour, t.minute, t.second);
-
+    Pit.initialize();
     Pci.initialize();
     Usb.initialize();
     sti();
diff --git a/src/hulk/pit.d b/src/hulk/pit.d
index 55d838d..33184e8 100644
--- a/src/hulk/pit.d
+++ b/src/hulk/pit.d
@@ -5,12 +5,13 @@ module hulk.pit;
 
 import hulk.cpu;
 import hulk.klog;
+import hulk.console;
 
 struct Pit
 {
     /** PIT input frequency in 1/1000 Hz. */
     private enum ulong PIT_FREQUENCY_1000HZ = 1_193_181_667u;
-    private enum ulong TARGET_INTERRUPT_HZ = 100u;
+    private enum ulong TARGET_INTERRUPT_HZ = 1000u;
     private enum ulong TARGET_INTERRUPT_1000HZ = TARGET_INTERRUPT_HZ * 1000u;
     private enum ulong PIT_DIVIDER = (PIT_FREQUENCY_1000HZ + TARGET_INTERRUPT_1000HZ / 2u) / TARGET_INTERRUPT_1000HZ;
 
@@ -28,8 +29,11 @@ struct Pit
     private enum ubyte MC_RATE_GENERATOR = 0x04u;
     private enum ubyte MC_BINARY = 0x00u;
 
+    private static __gshared ulong milliseconds;
+
     public static void initialize()
     {
+        Klog.writefln("\a3Initializing PIT");
         out8(PORT_MC, MC_CH_0 | MC_LO_HI | MC_RATE_GENERATOR | MC_BINARY);
         out8(PORT_CH_0, PIT_DIVIDER & 0xFFu);
         out8(PORT_CH_0, PIT_DIVIDER >> 8u);
@@ -37,6 +41,6 @@ struct Pit
 
     public static void isr()
     {
-        Klog.writefln("PIT ISR");
+        milliseconds++;
     }
 }
diff --git a/src/hulk/rtc.d b/src/hulk/rtc.d
index 0be2d13..9c14c30 100644
--- a/src/hulk/rtc.d
+++ b/src/hulk/rtc.d
@@ -79,11 +79,9 @@ struct Rtc
     public static void isr()
     {
         static __gshared ulong count;
-        static __gshared ulong seconds;
         count++;
         if ((count % 1024) == 0u)
         {
-            seconds++;
             Console.update_header();
         }
         eoi();