feat: acpi, apic, apic timer

src/arch/x86_64/pit.rs

@@ -0,0 +1,29 @@
+use core::arch::asm;
+
+use crate::arch::port::write_u8;
+
+const PIT_CHANNEL_0: u16 = 0x40;
+const PIT_COMMAND: u16 = 0x43;
+
+const CHANNEL_0: u8 = 0b00 << 6;
+// access mode = lobyte/hibyte
+const LOW_HIGH: u8 = 0b11 << 4;
+// interrupt on terminal count
+const MODE_0: u8 = 0b000 << 1;
+const BINARY: u8 = 0;
+
+pub const PIT_FREQUENCY: u64 = 1_193_182;
+pub const PIT_CALIBRATION_COUNT: u16 = u16::MAX;
+
+pub struct Pit;
+
+impl Pit {
+    pub fn start_one_shot(count: u16) {
+        unsafe {
+            write_u8(PIT_COMMAND, CHANNEL_0 | LOW_HIGH | MODE_0 | BINARY);
+
+            write_u8(PIT_CHANNEL_0, count as u8);
+            write_u8(PIT_CHANNEL_0, (count >> 8) as u8);
+        }
+    }
+}