Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757893AbYCUPDn (ORCPT ); Fri, 21 Mar 2008 11:03:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752871AbYCUPDf (ORCPT ); Fri, 21 Mar 2008 11:03:35 -0400 Received: from rtr.ca ([76.10.145.34]:4054 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752468AbYCUPDf (ORCPT ); Fri, 21 Mar 2008 11:03:35 -0400 Message-ID: <47E3CE44.4000000@rtr.ca> Date: Fri, 21 Mar 2008 11:03:32 -0400 From: Mark Lord Organization: Real-Time Remedies Inc. User-Agent: Thunderbird 2.0.0.12 (X11/20080213) MIME-Version: 1.0 To: Alan Cox Cc: Linus Torvalds , Bartlomiej Zolnierkiewicz , Anders Eriksson , "Rafael J. Wysocki" , Jens Axboe , Ingo Molnar , Linux Kernel Mailing List Subject: Re: Linux 2.6.25-rc4 References: <20080316140118.891732DC044@tippex.mynet.homeunix.org> <200803161907.04581.bzolnier@gmail.com> <20080316185602.79064f7c@core> <20080316203109.50e8c526@core> In-Reply-To: <20080316203109.50e8c526@core> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1787 Lines: 41 Alan Cox wrote: > On Sun, 16 Mar 2008 12:39:43 -0700 (PDT) > Linus Torvalds wrote: > >> >> On Sun, 16 Mar 2008, Alan Cox wrote: >>> No it doesn't. DRQ simply means "drive has more data for the controller >>> if you want it". Interrupts are controlled via IEN and the interrupt line. >> A _lot_ of chips require you to clear the DRQ by taking the data they >> have. > > Almost none and mostly very old ones. I'm not saying we shouldn't do it > (except where it hangs the hardware - hence the FIFO flag) but for the > traces presented and hardware reported it appears to be a bit of a red > herring. > >>> If the drive wants to give us data and we end the transaction that is >>> fine. In practice a tiny few devices crap themselves if we don't. >> More than a few tiny devices from what I remember. It tends to be the >> other way around - most devices do *not* want to get new commands until >> you've finished the previous one by draining the queues. > > Not in my experience having maintained a lot of ATA drivers for a very > long time. In fact the changes for draining the DRQ went into libata only > very recently because it was only when we had a distro sized userbase > with PATA devices that it became apparent that a few corner case problems > remained. .. Err.. I have a fairly modern PATA drive (160GB seagate 2.5") that gets pissed if we leave DRQ hanging. So it's not just something for old/obsolete drives. Or maybe it's the also-modern-ish ICH chipset that gets stuck. Whatever. -ml -- 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/