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 <st...@rowland.harvard.edu>
---
[as1714]
include/linux/usb/hcd.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
Index: usb-3.11/include/linux/usb/hcd.h
===================================================================
--- usb-3.11.orig/include/linux/usb/hcd.h
+++ usb-3.11/include/linux/usb/hcd.h
@@ -561,9 +561,8 @@ extern void usb_ep0_reinit(struct usb_de
* 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.
--
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