Commit 63fb3a28 authored Oct 11, 2013 by Alan Stern Committed by Greg Kroah-Hartman Oct 11, 2013

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>

parent 6ec4147e

include/linux/usb/hcd.h

+2 −3

Original line number	Diff line number	Diff line
		@@ -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.

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