Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267186AbUIAPny (ORCPT ); Wed, 1 Sep 2004 11:43:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267248AbUIAPnm (ORCPT ); Wed, 1 Sep 2004 11:43:42 -0400 Received: from daq3.if.pw.edu.pl ([194.29.174.23]:44672 "HELO milosz.na.pl") by vger.kernel.org with SMTP id S267205AbUIAPm1 (ORCPT ); Wed, 1 Sep 2004 11:42:27 -0400 From: Bartlomiej Zolnierkiewicz Reply-To: bzolnier@milosz.na.pl To: Mark Lord Subject: Re: [PATCH] Configure IDE probe delays Date: Wed, 1 Sep 2004 17:40:32 +0200 User-Agent: KMail/1.6.2 Cc: Lee Revell , Greg Stark , Denis Vlasenko , Alan Cox , Todd Poynor , Linux Kernel Mailing List , tim.bird@am.sony.com, dsingleton@mvista.com References: <20040730191100.GA22201@slurryseal.ddns.mvista.com> <200408272059.51779.bzolnier@elka.pw.edu.pl> <4135CC9E.5060905@rtr.ca> In-Reply-To: <4135CC9E.5060905@rtr.ca> MIME-Version: 1.0 Content-Disposition: inline Message-Id: <200409011740.32908.bzolnier@elka.pw.edu.pl> Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1388 Lines: 38 Jens come with this long time ago but IDE driver is not ready for it, there are some gaps to fill first. Anyway, thanks for reminding me about this. Cheers. On Wednesday 01 September 2004 15:20, Mark Lord wrote: > Bartlomiej Zolnierkiewicz wrote: > > > >>What determines whether 48 bit addressing will be used then? > > > > Availability of 48-bit addressing feature set and host capabilities > > (some don't support LBA48 when DMA is used etc.). > > I haven't examined the "released" IDE drivers in some time, > but one optimisation that can save a LOT of CPU usage > is for the driver to only use LBA48 *when necessary*, > and use LBA28 I/O otherwise. > > Each access to an IDE register typically chews up 600+ns, > or the equivalent of a couple thousand instruction executions > on a modern core. Avoiding LBA48 when it's not needed will > save four such accesses per I/O, or about 2.5us. > > LBA48 is only needed when (1) the sector count is greater than 256, > and/or (2) the ending sector number >= (1<<28). > > I regularly include this optimisation in the drivers I have been > working on since LBA48 first appeared. > > Cheers - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/