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authorAlan Stern <stern@rowland.harvard.edu>2013-10-11 11:28:02 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-11 16:37:45 -0700
commit63fb3a280061c5a1d9190015e5a074213f9d23c0 (patch)
treed19fa5a572dfc898651194b3ab50848035cc423a /include/linux/usb
parent6ec4147e7bdbde168f5bce30de5984aa4f971b22 (diff)
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>
Diffstat (limited to 'include/linux/usb')
-rw-r--r--include/linux/usb/hcd.h5
1 files changed, 2 insertions, 3 deletions
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index fc64b6825f5..dbe3cd19ffd 100644
--- 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.