stos/amd64: isa: Add legacy i8254 driver

Signed-off-by: Chloe M. <chloe@mensia.org>
2026-06-27 05:18:33 -05:00
parent ef72c9d6d5
commit 354cf87a16
2 changed files with 78 additions and 0 deletions
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  i8254 timer driver
+ * Author:       Chloe M.
+ */
+
+#include <machine/i8254.h>
+#include <machine/pio.h>
+
+USHORT
+MdPitGetCount(VOID)
+{
+    UCHAR Low, High;
+
+    MdOutb(I8254_COMMAND, 0x00);
+    Low = MdInb(0x40);
+    High = MdInb(0x40);
+    return (High << 8) | Low;
+}
+
+VOID
+MdPitSetCount(USHORT Value)
+{
+    MdOutb(I8254_COMMAND, 0x34);
+    MdOutb(0x40, Value & 0xFF);
+    MdOutb(0x40, (Value >> 8) & 0xFF);
+}
+
+VOID
+MdPitSetFrequency(UQUAD Frequency)
+{
+    UQUAD Divisor;
+
+    Divisor = I8254_DIVIDEND / Frequency;
+    if ((I8254_DIVIDEND % Frequency) > (Frequency / 2)) {
+        ++Divisor;
+    }
+
+    MdPitSetCount(Divisor);
+}