From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: Limiting DMA speeds for individual IDE drives Date: Tue, 08 Sep 2009 22:04:22 +0400 Message-ID: <4AA69CA6.9050909@ru.mvista.com> References: <20090908161204.GA3113@gambetta> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090908161204.GA3113@gambetta> Sender: linux-kernel-owner@vger.kernel.org To: Alan Stern Cc: Frederik Deweerdt , linux-ide@vger.kernel.org, Kernel development list List-Id: linux-ide@vger.kernel.org Hello. Frederik Deweerdt wrote: >>Is there any simple way to force the old IDE driver to limit the DMA >>speed for a particular device? No, you can only disable DMA totally, and then set the needed speed via hdparm. >>I've got a situation where a drive claims to be capable of supporting >>UDMA/100, but it's in a noisy environment and gets lots of errors at >>that speed. I'd like to limit it to UDMA/66 or even UDMA/33. Are you sure that it's all because of the noise and not a cable type misdetection? >>The hdparm command should be able to do this but I can't run it until >>the system has booted, by which time a bunch of CRC and possibly other >>errors have already occurred. Ideally it should be possible to limit >>the speed starting as early as device detection, but I can't find any >>way to do it. Is there support for such a thing or will I have to hack >>it in? > Does passing ide=nodma at bootime, and then having init set the DMA at > the right speed, would work? ide=nodma is now obsolete -- use ide_core.nodma=, instead. Read Documentation/ide/ide.txt before advising. ;-) > Regards, > Frederik WBR, Sergei