From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Clark Subject: Re: [PATCH] libata: warn if speed limited due to 40-wire cable (v2) Date: Sun, 04 Mar 2007 18:50:18 -0500 Message-ID: <45EB5B3A.2040009@seclark.us> References: <45DA44B4.6000209@shaw.ca> <45E8B42E.7010900@garzik.org> <20070303005433.714d75ad@lxorguk.ukuu.org.uk> <45E9DA80.2080109@tmr.com> <45EB0C95.1070505@seclark.us> <45EB4FA1.7020305@tmr.com> Reply-To: Stephen.Clark@seclark.us Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtpauth02.prod.mesa1.secureserver.net ([64.202.165.182]:56395 "HELO smtpauth02.prod.mesa1.secureserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752543AbXCDXuV (ORCPT ); Sun, 4 Mar 2007 18:50:21 -0500 In-Reply-To: <45EB4FA1.7020305@tmr.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Bill Davidsen Cc: Alan Cox , Jeff Garzik , Robert Hancock , linux-kernel , linux-ide@vger.kernel.org, Andrew Morton Bill Davidsen wrote: >Stephen Clark wrote: > > >>Bill Davidsen wrote: >> >> >> >>>Alan Cox wrote: >>> >>> >>> >>> >>>>>it seems broken to manipulate xfer_mask after returning from the >>>>>driver's ->mode_filter hook. >>>>> >>>>>this patch is more than just a speed-limited warning printk, afaics >>>>> >>>>> >>>>> >>>>I actually suggested that order because the only way the printk can be >>>>done correctly is for it to be the very last test made. Since the mode >>>>filter is not told what mode will be used but just subtracts modes that >>>>are not allowed this should be safe. >>>> >>>> >>>> >>>Far better to have a drive which works slowly than one which works >>>unreliably. >>> >>> >>> >>> >>> >>That would be true if the 40 wire detection was 100% accurate! >> >> >The statement is completely correct, even though the detection may not >be. ;-) > >With the current set(s) of patches to do better detection, cable >evaluation should be better. But even if not, a slow system is more >useful than one which doesn't work, crashes because of swap i/o errors, etc. > > > I have had problems with cable detection on my previous laptop and my current laptop. It almost made my systems unusable. On my current laptop I was getting a thruput of a little over 1 mbps instead of the 44 mbps I get with udma set to the correct value. It took hours to upgrade my laptop from fc5 to fc6 because of this mis detection. -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." (Ben Franklin) "The course of history shows that as a government grows, liberty decreases." (Thomas Jefferson)