From: Alan Stern <stern@rowland.harvard.edu>
Date: Fri, 28 Sep 2012 20:01:40 +0000 (-0400)
Subject: EHCI: replace mult/div with bit-mask operation
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=72675479925f53af051ae8a78bcfafeaa47b3eef;p=linux.git

EHCI: replace mult/div with bit-mask operation

This patch (as1610) replaces multiplication and divison operations in
ehci-hcd's isochronous scheduling code with a bit-mask operation,
taking advantage of the fact that isochronous periods are always
powers of 2.

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

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index b764cab2ab9ac..e08e65d8e0047 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1416,7 +1416,7 @@ iso_stream_schedule (
 
 		/* Behind the scheduling threshold?  Assume URB_ISO_ASAP. */
 		if (unlikely(start < next))
-			start += period * DIV_ROUND_UP(next - start, period);
+			start += (next - start + period - 1) & (- period);
 
 		start += base;
 	}