From owner-freebsd-current@FreeBSD.ORG Fri Jul 30 19:03:34 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id F0A9516A4CE; Fri, 30 Jul 2004 19:03:33 +0000 (GMT) Received: from out009.verizon.net (out009pub.verizon.net [206.46.170.131]) by mx1.FreeBSD.org (Postfix) with ESMTP id 61F7543D62; Fri, 30 Jul 2004 19:03:33 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from [192.168.1.3] ([68.161.100.95]) by out009.verizon.net (InterMail vM.5.01.06.06 201-253-122-130-106-20030910) with ESMTP id <20040730190251.ICXH23440.out009.verizon.net@[192.168.1.3]>; Fri, 30 Jul 2004 14:02:51 -0500 Message-ID: <410A9B58.8000502@mac.com> Date: Fri, 30 Jul 2004 15:02:48 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.1) Gecko/20040707 X-Accept-Language: en-us, en MIME-Version: 1.0 To: =?ISO-8859-1?Q?S=F8ren_Schmidt?= References: <410A3833.7030502@portaone.com> <410A47C7.1080808@DeepCore.dk> In-Reply-To: <410A47C7.1080808@DeepCore.dk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Authentication-Info: Submitted using SMTP AUTH at out009.verizon.net from [68.161.100.95] at Fri, 30 Jul 2004 14:02:51 -0500 cc: Maxim Sobolev cc: current@freebsd.org cc: release@freebsd.org Subject: Re: Is there still sufficient reason for hw.ata.atapi_dma being 0 by default? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Jul 2004 19:03:34 -0000 Søren Schmidt wrote: > Maxim Sobolev wrote: >> Since high-speed CD-RW/DVD-RW recorders (32x - 52x) are commodity now >> IMO it makes sense to review hw.ata.atapi_dma default of 0, since >> apparently PIO mode can't support necessary sustained data transfer >> rates anymore. For example I had had problems burning RWs on 16-24x >> with several drives in PIO mode, which gone when I've switched to DMA. Before CD burners became common, having this sysctl default to zero was almost entirely harmless: people would simply read from CD-ROM drives slower than optimal. If we change the default to one, people with fast burners will no longer generate coasters by default too. In other words, Maxim has provided a pretty good reason for changing the default of atapi_dma, I think. :-) > Hmm, things are still messy, but most drives that support UDMA33 can do > ATAPI dma. However, that is only part of the equation, the chipset has > its hands in there as well, and unfortunatly there seems to be no good > way to detect when it works and when it doesnt. If the chipset is broken, why doesn't it default to using PIO4 rather than UDMA? :-) Anyway, doesn't there exist fallback code in dev/ata/ata-disk.c: /* if this is a UDMA CRC error, reinject request */ [ ... ] printf(" falling back to PIO mode\n"); ...which will switch a device generating errors from UDMA mode to PIO? Can this check also turn off using atapi_dma (if using PIO doesn't already imply not using DMA)? -- -Chuck