feat(drivers): remap PIC and drive PIT at 100 Hz

include/pic.h

@@ -0,0 +1,11 @@
+#ifndef FROSTBYTE_PIC_H
+#define FROSTBYTE_PIC_H
+
+#include "types.h"
+
+void picRemap(void);
+void picSendEoi(uint8 irq);
+void picSetMask(uint8 irq);
+void picClearMask(uint8 irq);
+
+#endif

include/pit.h

@@ -0,0 +1,11 @@
+#ifndef FROSTBYTE_PIT_H
+#define FROSTBYTE_PIT_H
+
+#include "types.h"
+
+void pitInit(uint32 frequency);
+void pitTick(void);
+uint64 pitTicks(void);
+uint32 pitFrequency(void);
+
+#endif

src/pic.c

@@ -0,0 +1,63 @@
+#include "pic.h"
+#include "ports.h"
+
+#define picMasterCommand 0x20
+#define picMasterData 0x21
+#define picSlaveCommand 0xA0
+#define picSlaveData 0xA1
+#define picEoi 0x20
+
+#define icw1Init 0x11
+#define icw4Mode 0x01
+
+#define masterVectorBase 0x20
+#define slaveVectorBase 0x28
+
+void picRemap(void)
+{
+    uint8 masterMask = inb(picMasterData);
+    uint8 slaveMask = inb(picSlaveData);
+
+    outb(picMasterCommand, icw1Init);
+    ioWait();
+    outb(picSlaveCommand, icw1Init);
+    ioWait();
+    outb(picMasterData, masterVectorBase);
+    ioWait();
+    outb(picSlaveData, slaveVectorBase);
+    ioWait();
+    outb(picMasterData, 0x04);
+    ioWait();
+    outb(picSlaveData, 0x02);
+    ioWait();
+    outb(picMasterData, icw4Mode);
+    ioWait();
+    outb(picSlaveData, icw4Mode);
+    ioWait();
+
+    outb(picMasterData, masterMask);
+    outb(picSlaveData, slaveMask);
+}
+
+void picSendEoi(uint8 irq)
+{
+    if (irq >= 8)
+        outb(picSlaveCommand, picEoi);
+    outb(picMasterCommand, picEoi);
+}
+
+void picSetMask(uint8 irq)
+{
+    uint16 port = irq < 8 ? picMasterData : picSlaveData;
+    uint8 bit = irq < 8 ? irq : (uint8)(irq - 8);
+    uint8 value = inb(port) | (uint8)(1 << bit);
+    outb(port, value);
+}
+
+void picClearMask(uint8 irq)
+{
+    uint16 port = irq < 8 ? picMasterData : picSlaveData;
+    uint8 bit = irq < 8 ? irq : (uint8)(irq - 8);
+    uint8 value = inb(port) & (uint8)~(1 << bit);
+    outb(port, value);
+}

src/pit.c

@@ -0,0 +1,34 @@
+#include "pit.h"
+#include "ports.h"
+
+#define pitChannel0 0x40
+#define pitCommand 0x43
+#define pitBaseFrequency 1193182
+
+static volatile uint64 tickCount;
+static uint32 configuredFrequency;
+
+void pitInit(uint32 frequency)
+{
+    configuredFrequency = frequency;
+    uint32 divisor = pitBaseFrequency / frequency;
+
+    outb(pitCommand, 0x36);
+    outb(pitChannel0, (uint8)(divisor & 0xFF));
+    outb(pitChannel0, (uint8)((divisor >> 8) & 0xFF));
+}
+
+void pitTick(void)
+{
+    tickCount++;
+}
+
+uint64 pitTicks(void)
+{
+    return tickCount;
+}
+
+uint32 pitFrequency(void)
+{
+    return configuredFrequency;
+}