X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;f=src%2Ftimer.c;fp=src%2Ftimer.c;h=937b56d59f9ff39ab2ff2d6b427af09c2b0e7466;hb=a2f94f569a4c99204de02814a20098a71527e913;hp=0000000000000000000000000000000000000000;hpb=d1e8a437c1fab4535f82c4c214ec3330ac32e48d;p=bootcensus

diff --git a/src/timer.c b/src/timer.c
new file mode 100644
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++;
+}
+*/