1 files changed, 72 insertions, 0 deletions
diff --git a/src/i8254.c b/src/i8254.c
new file mode 100644
index 0000000..fc4f48d
--- /dev/null
+++ b/src/i8254.c
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <lib/macros.h>
+
+#include "cpu.h"
+#include "i8254.h"
+#include "io.h"
+#include "thread.h"
+
+#define I8254_FREQ                  1193182
+
+#define I8254_PORT_CHANNEL0         0x40
+#define I8254_PORT_MODE             0x43
+
+#define I8254_CONTROL_BINARY        0x00
+#define I8254_CONTROL_RATE_GEN      0x04
+#define I8254_CONTROL_RW_LSB        0x10
+#define I8254_CONTROL_RW_MSB        0x20
+#define I8254_CONTROL_COUNTER0      0x00
+
+#define I8254_INITIAL_COUNT         DIV_CEIL(I8254_FREQ, THREAD_SCHED_FREQ)
+
+#define I8254_IRQ                   0
+
+static void
+i8254_irq_handler(void *arg)
+{
+    (void)arg;
+    thread_report_tick();
+}
+
+void
+i8254_setup(void)
+{
+    uint16_t value;
+
+    /*
+     * Program the timer to raise an interrupt at the scheduling frequency.
+     */
+
+    io_write(I8254_PORT_MODE, I8254_CONTROL_COUNTER0
+                              | I8254_CONTROL_RW_MSB
+                              | I8254_CONTROL_RW_LSB
+                              | I8254_CONTROL_RATE_GEN
+                              | I8254_CONTROL_BINARY);
+
+    value = I8254_INITIAL_COUNT;
+    io_write(I8254_PORT_CHANNEL0, value & 0xff);
+    io_write(I8254_PORT_CHANNEL0, value >> 8);
+
+    cpu_irq_register(I8254_IRQ, i8254_irq_handler, NULL);
+}