From 974eba39dfe2fe46f2fa2ce244c6425714e96bad Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Sun, 8 Nov 2026 04:12:44 +0800
Subject: [mubios] Implement the PIC and PIT.

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>
---
 mubios/core/post.c    |  5 +++-
 mubios/drivers/pic.c  | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++
 mubios/drivers/pit.c  | 45 +++++++++++++++++++++++++++++++++++
 mubios/include/bios.h |  3 +++
 4 files changed, 117 insertions(+), 1 deletion(-)
 create mode 100644 mubios/drivers/pic.c
 create mode 100644 mubios/drivers/pit.c

diff --git a/mubios/core/post.c b/mubios/core/post.c
index 69ad7e7..afad12b 100644
--- a/mubios/core/post.c
+++ b/mubios/core/post.c
@@ -30,5 +30,8 @@ post_main (void)
   memory_init ();
   bda_init ();
 
-  serial_write ("mubios: memory initialized\r\n");
+  pic_init ();
+  pit_init ();
+
+  serial_write ("mubios: PIC/PIT initialized\r\n");
 }
diff --git a/mubios/drivers/pic.c b/mubios/drivers/pic.c
new file mode 100644
index 0000000..099cee8
--- /dev/null
+++ b/mubios/drivers/pic.c
@@ -0,0 +1,65 @@
+/*
+ RCC-Project
+
+ Copyright (C) 2026 Richard Qin
+
+ This file is part of RCC-Project.
+
+ RCC-Project is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your option) any
+ later version.
+
+ RCC-Project is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ RCC-Project; see the file COPYING.  If not see
+ <http://www.gnu.org/licenses/>.
+ */
+
+#include "bios.h"
+#include "io.h"
+
+#define PIC1_COMMAND 0x0020u
+#define PIC1_DATA    0x0021u
+#define PIC2_COMMAND 0x00A0u
+#define PIC2_DATA    0x00A1u
+
+#define PIC_ICW1_INIT 0x11u
+#define PIC_ICW4_8086 0x01u
+
+#define PIC1_VECTOR_BASE 0x08u
+#define PIC2_VECTOR_BASE 0x70u
+
+#define PIC1_CASCADE_ID 0x04u
+#define PIC2_CASCADE_ID 0x02u
+
+#define PIC1_MASK_DEFAULT 0xFBu
+#define PIC2_MASK_DEFAULT 0xFFu
+
+void
+pic_init (void)
+{
+  io_out8 (PIC1_COMMAND, PIC_ICW1_INIT);
+  io_out8(PIC2_COMMAND, PIC_ICW1_INIT);
+
+  io_out8(PIC1_DATA, PIC1_VECTOR_BASE);
+  io_out8 (PIC2_DATA, PIC2_VECTOR_BASE);
+
+  io_out8(PIC1_DATA, PIC1_CASCADE_ID);
+  io_out8 (PIC2_DATA, PIC2_CASCADE_ID);
+
+  io_out8(PIC1_DATA, PIC_ICW4_8086);
+  io_out8 (PIC2_DATA, PIC_ICW4_8086);
+
+  /*
+   * Keep the cascade line enabled.
+   * All actual hardware IRQ lines remain masked.
+   */
+  io_out8(PIC1_DATA, PIC1_MASK_DEFAULT);
+  io_out8 (PIC2_DATA, PIC2_MASK_DEFAULT);
+  
+}
+
diff --git a/mubios/drivers/pit.c b/mubios/drivers/pit.c
new file mode 100644
index 0000000..4213940
--- /dev/null
+++ b/mubios/drivers/pit.c
@@ -0,0 +1,45 @@
+/*
+ RCC-Project
+
+ Copyright (C) 2026 Richard Qin
+
+ This file is part of RCC-Project.
+
+ RCC-Project is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your option) any
+ later version.
+
+ RCC-Project is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ RCC-Project; see the file COPYING.  If not see
+ <http://www.gnu.org/licenses/>.
+ */
+
+#include "bios.h"
+#include "io.h"
+
+#define PIT_COUNTER0 0x0040u
+#define PIT_COMMAND  0x0043u
+
+#define PIT_SELECT_CHANNEL0 0x00u
+#define PIT_ACCESS_WORD     0x30u
+#define PIT_MODE_2          0x04u
+#define PIT_BINARY 0x00u
+
+#define PIT_COMMAND_CHANNEL0_MODE2                                            \
+  (PIT_SELECT_CHANNEL0 | PIT_ACCESS_WORD | PIT_MODE_2 | PIT_BINARY)
+
+void pit_init(void)
+{
+  io_out8 (PIT_COMMAND, PIT_COMMAND_CHANNEL0_MODE2);
+
+  /*
+   * A divisor of zero represents 65536.
+   */
+  io_out8 (PIT_COUNTER0, 0x00u);
+  io_out8 (PIT_COUNTER0, 0x00u);  
+}
diff --git a/mubios/include/bios.h b/mubios/include/bios.h
index c3b5026..3df9846 100644
--- a/mubios/include/bios.h
+++ b/mubios/include/bios.h
@@ -44,4 +44,7 @@ void serial_init (void);
 void serial_putc (u8 value);
 void serial_write (const char *text);
 
+void pic_init (void);
+void pit_init (void);
+
 #endif // MUBIOS_BIOS_H
-- 
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