From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752129Ab1CZN7A (ORCPT ); Sat, 26 Mar 2011 09:59:00 -0400 Received: from mail.bisel.ru ([80.93.56.210]:39499 "EHLO mail.bisel.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926Ab1CZN67 (ORCPT ); Sat, 26 Mar 2011 09:58:59 -0400 X-Envelope-Recipient: alan@lxorguk.ukuu.org.uk X-Envelope-Recipient: jgarzik@pobox.com X-Envelope-Recipient: linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Date: Sat, 26 Mar 2011 16:58:55 +0300 From: igor@novg.net To: Alan Cox Cc: , Subject: Re: [PATCH 2.6.38.1] =?UTF-8?Q?pata=5Fit=38=32=31x=3A=20Add=20mod?= =?UTF-8?Q?ule=20param=20to=20force=20UDMA=20on=20Vortex=38=36SX?= In-Reply-To: <20110326125441.3e628850@lxorguk.ukuu.org.uk> References: <89bf4e2c74a16f130208a485c6eafd77@novg.net> <20110326125441.3e628850@lxorguk.ukuu.org.uk> Message-ID: <90c1a5f93e6d67aec9f67a1d4c0deb86@novg.net> User-Agent: Roundcube Webmail/0.5.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 26 Mar 2011 12:54:41 +0000, Alan Cox wrote: >> May be there are errors with pure IDE devices or with older >> revisions >> of Vortex86SX >> boards, i do no know. But for my device i have 2x improvement in >> I/O >> speed when >> enabling UDMA/33 instead of MWDMA, so i think this parameter would >> be >> useful. > > "I do not know" is not a good basis for hacking storage code, > particularly if it was to turn out that the reason was something like > silent data corruption (eg as with UDMA on the old OSB4 controllers > in > some cases) > Well, by "i do not know" i meant that i do not have other (older) DMP hardware, nor do i have means to connect pure IDE device to my device (DMP-2300). I just can state that i was having a root FS on a CompactFlash for quite a long time with UDMA enabled, and i have not observed any problems, and have seen no signs of data corruption either. I am just proposing to give users an option to enable UDMA at their own risk, maybe add comment stating that enabling this option may or may not cause silent data corruption. Or maybe to add this as a sub-option to the driver in Kconfig to switch on/off at compile time with detailed description under ---help--- > The change came via DMP signoff (the manufacturer) so any adjustment > of > this sort of checking really ought to go via DMP as well. > >> Also fix to initialize default value for parameter 'noraid'. > > This does not need initialising - C guarantees static variables start > at > zero. If that makes a difference you have other problems. Sorry, my bad. > So NAK this. > > Although if you want to take it up with DMP and find out if they have > updated rules or checks that want pushing that might be useful. No, i do not intend to contact them, i just wanted people to have an on/off switch in kernel, not to push this patch by all means necessary. If this option is considered by community unneeded, i'll just have to patch my own kernel with every upgrade :) > Alan