USB: NS_TO_US should round up

Host controller drivers use the NS_TO_US macro to convert transaction
times, which are computed in nanoseconds, to microseconds for
scheduling.  Periodic scheduling requires worst-case estimates, but
the macro does its conversion using round-to-nearest.  This patch
changes it to use round-up, giving a correct worst-case value.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index fc64b6825f5e4c21f2a85f99d59e6090fd39c2ca..dbe3cd19ffd88a232976f2b2333e6b4f6a4120f9 100644 (file)
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -564,9 +564,8 @@ extern void usb_ep0_reinit(struct usb_device *);
                 * of (7/6 * 8 * bytecount) = 9.33 * bytecount */
                /* bytecount = data payload byte count */
 
-#define NS_TO_US(ns)   ((ns + 500L) / 1000L)
-                       /* convert & round nanoseconds to microseconds */
-
+#define NS_TO_US(ns)   DIV_ROUND_UP(ns, 1000L)
+                       /* convert nanoseconds to microseconds, rounding up */
 
 /*
  * Full/low speed bandwidth allocation constants/support.