Add pit and rtc modules

src/hulk/pit.d

@@ -0,0 +1,42 @@
+/**
+ * PIT (Programmable Interval Timer) functionality.
+ */
+module hulk.pit;
+
+import hulk.cpu;
+import hulk.klog;
+
+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_1000HZ = TARGET_INTERRUPT_HZ * 1000u;
+    private enum ulong PIT_DIVIDER = (PIT_FREQUENCY_1000HZ + TARGET_INTERRUPT_1000HZ / 2u) / TARGET_INTERRUPT_1000HZ;
+
+    /** PIT channel 0 I/O port. */
+    private enum ubyte PORT_CH_0 = 0x40u;
+    /** PIT channel 1 I/O port. */
+    private enum ubyte PORT_CH_1 = 0x41u;
+    /** PIT channel 2 I/O port. */
+    private enum ubyte PORT_CH_2 = 0x42u;
+    /** PIT mode/command register I/O port. */
+    private enum ubyte PORT_MC = 0x43u;
+
+    private enum ubyte MC_CH_0 = 0x00u;
+    private enum ubyte MC_LO_HI = 0x30u;
+    private enum ubyte MC_RATE_GENERATOR = 0x04u;
+    private enum ubyte MC_BINARY = 0x00u;
+
+    public static void initialize()
+    {
+        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);
+    }
+
+    public static void isr()
+    {
+        klog.writefln("PIT ISR");
+    }
+}