x86: new architecture

Merge 32-bit IA-32 (i386) and 64-bit AMD64 (amd64) code into one common
architecture. The amd64 variant isn't functional yet.

1 files changed, 88 insertions, 0 deletions

diff --git a/arch/x86/machine/pit.c b/arch/x86/machine/pit.c
new file mode 100644
index 0000000..e5113ce
--- /dev/null
+++ b/arch/x86/machine/pit.c
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2011, 2012 Richard Braun.
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <kern/init.h>
+#include <lib/assert.h>
+#include <machine/io.h>
+#include <machine/pit.h>
+
+/*
+ * I/O ports.
+ */
+#define PIT_PORT_COUNTER0   0x40
+#define PIT_PORT_MODE       0x43
+
+/*
+ * Mode control register bits.
+ */
+#define PIT_MODE_LATCH      0x00
+#define PIT_MODE_RATE_GEN   0x04
+#define PIT_MODE_RW_LSB     0x10
+#define PIT_MODE_RW_MSB     0x20
+
+/*
+ * Native timer frequency.
+ */
+#define PIT_FREQ 1193182
+
+/*
+ * Maximum value of a counter.
+ */
+#define PIT_MAX_COUNT 0xffff
+
+void __init
+pit_setup(void)
+{
+    io_write_byte(PIT_PORT_MODE, PIT_MODE_RATE_GEN | PIT_MODE_RW_LSB
+                                 | PIT_MODE_RW_MSB);
+    io_write_byte(PIT_PORT_COUNTER0, PIT_MAX_COUNT & 0xff);
+    io_write_byte(PIT_PORT_COUNTER0, PIT_MAX_COUNT >> 8);
+}
+
+static unsigned int
+pit_read(void)
+{
+    unsigned int low, high;
+
+    io_write_byte(PIT_PORT_MODE, PIT_MODE_LATCH);
+    low = io_read_byte(PIT_PORT_COUNTER0);
+    high = io_read_byte(PIT_PORT_COUNTER0);
+    return (high << 8) | low;
+}
+
+void
+pit_delay(unsigned long usecs)
+{
+    long total, prev, count, diff;
+
+    assert(usecs != 0);
+
+    /* TODO Avoid 64-bits conversion if result is known not to overflow */
+    total = (long)(((long long)usecs * PIT_FREQ + 999999) / 1000000);
+    prev = pit_read();
+
+    do {
+        count = pit_read();
+        diff = prev - count;
+        prev = count;
+
+        if (diff < 0)
+            diff += PIT_MAX_COUNT;
+
+        total -= diff;
+    } while (total > 0);
+}