Fix DELAY function to use the RPCC cycle counter register.

svn path=/head/; revision=60200

sys/alpha/alpha/machdep.c

@@ -1130,17 +1130,44 @@ bzero(void *buf, size_t len)
 	}
 }
 
-/*
- * Wait "n" microseconds.
- */
 void
 DELAY(int n)
 {
-#ifndef SIMOS
-	long N = cycles_per_usec * (n);
+#ifndef	SIMOS
+	unsigned long pcc0, pcc1, curcycle, cycles;
+        int usec;
 
-	while (N > 0)				/* XXX */
-		N -= 3;				/* XXX */
+	if (n == 0)
+		return;
+
+        pcc0 = alpha_rpcc() & 0xffffffffUL;
+	cycles = 0;
+	usec = 0;
+
+        while (usec <= n) {
+		/*
+		 * Get the next CPU cycle count;
+		 */
+		pcc1 = alpha_rpcc() & 0xffffffffUL;
+		if (pcc1 < pcc0) {
+			curcycle = (pcc1 + 0x100000000UL) - pcc0;
+		} else {
+			curcycle = pcc1 - pcc0;
+		}
+
+		/*
+		 * We now have the number of processor cycles since we
+		 * last checked. Add the current cycle count to the
+		 * running total. If it's over cycles_per_usec, increment
+		 * the usec counter.
+		 */
+		cycles += curcycle;
+		while (cycles > cycles_per_usec) {
+			usec++;
+			cycles -= cycles_per_usec;
+		}
+		pcc0 = pcc1;
+        }
 #endif
 }