From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 5/7] sfc: Work around XMAC bug causing packet loss with some peers Date: Wed, 26 Aug 2009 18:04:20 -0700 (PDT) Message-ID: <20090826.180420.114585490.davem@davemloft.net> References: <1251310679.27345.17.camel@achroite> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-net-drivers@solarflare.com To: bhutchings@solarflare.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:53167 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754520AbZH0BEG (ORCPT ); Wed, 26 Aug 2009 21:04:06 -0400 In-Reply-To: <1251310679.27345.17.camel@achroite> Sender: netdev-owner@vger.kernel.org List-ID: From: Ben Hutchings Date: Wed, 26 Aug 2009 19:17:59 +0100 > Received frames must be re-clocked by the local XGXS to the 156.25 MHz > (DDR) clock of the XGMII. If the remote clock is slightly faster this > can reduce a minimum IPG of 64 bit-times (1 cycle) to 32 bit-times > (half a cycle). If the XMAC detects that a frame has reached the > maximum RX frame length in the same cycle that it receives one of > these reduced IPGs, it may miss the IPG, causing two valid frames to > be treated as a single invalid frame (over-length with bad CRC). > > We work around this by increasing the maximum RX frame length so that > peers with matched MTU will not provoke this bug. > > Signed-off-by: Ben Hutchings Applied.