interrupts, timer, keyboard, segments, lots of kernel code

[bootcensus] / src / timer.c

diff --git a/src/timer.c b/src/timer.c
new file mode 100644 (file)
index 0000000..937b56d
--- /dev/null
+++ b/src/timer.c
@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include "intr.h"
+#include "asmops.h"
+#include "timer.h"
+#include "config.h"
+
+/* frequency of the oscillator driving the 8254 timer */
+#define OSC_FREQ_HZ            1193182
+
+/* macro to divide and round to the nearest integer */
+#define DIV_ROUND(a, b) ((a) / (b) + ((a) % (b)) / ((b) / 2))
+
+/* I/O ports connected to the 8254 */
+#define PORT_DATA0     0x40
+#define PORT_DATA1     0x41
+#define PORT_DATA2     0x42
+#define PORT_CMD       0x43
+
+/* command bits */
+#define CMD_CHAN0                      0
+#define CMD_CHAN1                      (1 << 6)
+#define CMD_CHAN2                      (2 << 6)
+#define CMD_RDBACK                     (3 << 6)
+
+#define CMD_LATCH                      0
+#define CMD_ACCESS_LOW         (1 << 4)
+#define CMD_ACCESS_HIGH                (2 << 4)
+#define CMD_ACCESS_BOTH                (3 << 4)
+
+#define CMD_OP_INT_TERM                0
+#define CMD_OP_ONESHOT         (1 << 1)
+#define CMD_OP_RATE                    (2 << 1)
+#define CMD_OP_SQWAVE          (3 << 1)
+#define CMD_OP_SOFT_STROBE     (4 << 1)
+#define CMD_OP_HW_STROBE       (5 << 1)
+
+#define CMD_MODE_BIN           0
+#define CMD_MODE_BCD           1
+
+
+#define MSEC_TO_TICKS(ms)      ((ms) * TICK_FREQ_HZ / 1000)
+
+struct timer_event {
+       int dt; /* remaining ticks delta from the previous event */
+       struct timer_event *next;
+};
+
+/* defined in intr_asm.S */
+void intr_entry_fast_timer(void);
+
+static struct timer_event *evlist;
+
+
+void init_timer(void)
+{
+       /* calculate the reload count: round(osc / freq) */
+       int reload_count = DIV_ROUND(OSC_FREQ_HZ, TICK_FREQ_HZ);
+
+       /* set the mode to square wave for channel 0, both low
+        * and high reload count bytes will follow...
+        */
+       outb(CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE, PORT_CMD);
+
+       /* write the low and high bytes of the reload count to the
+        * port for channel 0
+        */
+       outb(reload_count & 0xff, PORT_DATA0);
+       outb((reload_count >> 8) & 0xff, PORT_DATA0);
+
+       /* set the timer interrupt handler */
+       /*interrupt(IRQ_TO_INTR(0), timer_handler);*/
+       /* set low level fast timer interrupt routine directly in the IDT */
+       set_intr_entry(IRQ_TO_INTR(0), intr_entry_fast_timer);
+}
+
+/*
+static void timer_handler(int inum)
+{
+       nticks++;
+}
+*/