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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>
This commit is contained in:
Alan Stern 2013-10-11 11:28:02 -04:00 committed by Greg Kroah-Hartman
parent 6ec4147e7b
commit 63fb3a2800
1 changed files with 2 additions and 3 deletions
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5
include/linux/usb/hcd.h
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@ -564,9 +564,8 @@ extern void usb_ep0_reinit(struct usb_device *);
* of (7/6 * 8 * bytecount) = 9.33 * bytecount */ * of (7/6 * 8 * bytecount) = 9.33 * bytecount */
/* bytecount = data payload byte count */ /* bytecount = data payload byte count */
#define NS_TO_US(ns) ((ns + 500L) / 1000L) #define NS_TO_US(ns) DIV_ROUND_UP(ns, 1000L)
/* convert & round nanoseconds to microseconds */ /* convert nanoseconds to microseconds, rounding up */
/* /*
* Full/low speed bandwidth allocation constants/support. * Full/low speed bandwidth allocation constants/support.