Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760168AbZCaOGi (ORCPT ); Tue, 31 Mar 2009 10:06:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758551AbZCaOGP (ORCPT ); Tue, 31 Mar 2009 10:06:15 -0400 Received: from yw-out-2324.google.com ([74.125.46.29]:40277 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757371AbZCaOGN (ORCPT ); Tue, 31 Mar 2009 10:06:13 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type:content-transfer-encoding; b=FgxodDBWtmp/6oQFmlBa2KgZ6S1Y6+HJQriEWPBEkeEv6P/DrEmPEkl7+Jxx667Iij KEOB4mk5kYgGd8ZCdoR46dROl/OGIFjxLmWgvkKidwJybfpceAaXzhUOxi5OZe4l/KDS nbgyY45/mCg7+OU61OeRh0XNxqXKy2VLqRA78= MIME-Version: 1.0 Reply-To: petkovbb@gmail.com In-Reply-To: <49D20E1B.7010104@nessie.de> References: <49CFCB2A.4020505@nessie.de> <49CFEA24.10700@nessie.de> <20090330072713.GA13776@liondog.tnic> <200903302228.54601.bzolnier@gmail.com> <20090331074508.GA16403@liondog.tnic> <20090331122820.167d52e5@the-village.bc.nu> <49D20E1B.7010104@nessie.de> Date: Tue, 31 Mar 2009 16:06:11 +0200 Message-ID: <9ea470500903310706i23e2225fo42ff17f14c277594@mail.gmail.com> Subject: Re: Bug in 2.6.29 ide-cd: Kernel freeze: bisected + unacceptable workaround From: Borislav Petkov To: Michael Roth Cc: Alan Cox , Bartlomiej Zolnierkiewicz , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1833 Lines: 39 Hi, On Tue, Mar 31, 2009 at 2:35 PM, Michael Roth wrote: >>> take it ok. Also, if I remember correctly, the original ide-cd behavior >>> was to issue the command and _then_ start DMA so we're back to that. I >>> guess now we should be concerned whether the other ATAPI devices can >>> handle the reverse situation where you first issue a command and _then_ >>> start DMA.. Hmm... >> >> Most devices don't care but you do need to follow the exact ATAPI spec. >> If you search way back through the archives you'll find long discussions >> on this during either 2.4 or 2.2 when HP hit problems caused by us >> turning DMA on too early. > > AFAIK, the old bevavior was to start DMA _after_ issuing the command _only_ > for CD-drives and for the remaining ide devices the other way around, > why not just restore the old behavior and do the DMA after command only > for CD-drives? because common atapi code should adhere to the spec, as Alan said, no matter whether it is a cd or a floppy or [you name it]-drive. @Alan: I guess you refer to http://lkml.indiana.edu/hypermail/linux/kernel/0305.1/2241.html, for example. I think I'll be on the safe side when I turn on DMA _after_ writing the ATAPI command packet into the data register - it is the correct order of steps according to the ATA spec. So, if there are devices which still choke on that, then they're simply buggy and those will hopefully be a small number so that a blacklist with a flag as a workaround would be more or less ok for them - we do that for other b0rked devices anyway. -- Regards/Gruss, Boris -- 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/