1 files changed, 43 insertions, 0 deletions
diff --git a/udelay.c b/udelay.c
new file mode 100644
index 0000000..9674bbe
--- /dev/null
+++ b/udelay.c
@@ -0,0 +1,43 @@
+#include <sys/time.h>
+#include <stdio.h>
+
+// count to a billion. Time it. If it's < 1 sec, count to 10B, etc.
+unsigned long micro = 1;
+
+void myusec_delay(int time)
+{
+	volatile unsigned long i;
+	for(i = 0; i < time * micro; i++)
+		;
+}
+
+void myusec_calibrate_delay()
+{
+	int count = 1000;
+	unsigned long timeusec;
+	struct timeval start, end;
+	int ok = 0;
+	void myusec_delay(int time);
+
+	printf("Setting up microsecond timing loop\n");
+	while (!ok) {
+		//fprintf(stderr, "Try %d\n", count);
+		gettimeofday(&start, 0);
+		myusec_delay(count);
+		gettimeofday(&end, 0);
+		timeusec = 1000000 * (end.tv_sec - start.tv_sec ) + 
+			(end.tv_usec - start.tv_usec);
+		//fprintf(stderr, "timeusec is %d\n", timeusec);
+		count *= 2;
+		if (timeusec < 1000000/4)
+			continue;
+		ok = 1;
+	}
+
+	// compute one microsecond. That will be count / time
+	micro = count / timeusec;
+
+	fprintf(stderr, "%ldM loops per second\n", (unsigned long)micro);
+
+
+}