From mboxrd@z Thu Jan 1 00:00:00 1970 From: Frederik Deweerdt Subject: Re: Limiting DMA speeds for individual IDE drives Date: Tue, 8 Sep 2009 16:24:34 +0000 Message-ID: <20090908161204.GA3113@gambetta> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Alan Stern Cc: linux-ide@vger.kernel.org, Kernel development list List-Id: linux-ide@vger.kernel.org On Tue, Sep 08, 2009 at 12:03:48PM -0400, Alan Stern wrote: > Is there any simple way to force the old IDE driver to limit the DMA > speed for a particular device? > > 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. > > 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? Regards, Frederik