From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH 02/02] sata_mv: warn on PIO with multiple DRQs Date: Wed, 18 Jun 2008 20:29:58 -0400 Message-ID: <4859A886.8000509@pobox.com> References: <485933A4.3010409@rtr.ca> <4859340E.60203@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:58755 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757094AbYFSAaC (ORCPT ); Wed, 18 Jun 2008 20:30:02 -0400 In-Reply-To: <4859340E.60203@rtr.ca> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Mark Lord Cc: IDE/ATA development list , Tejun Heo Mark Lord wrote: > Chip errata sometimes prevents reliable use of PIO commands which involve > more than a single DRQ (data request). In normal operation, libata should > not generate such PIO commands (uses DMA instead), but they could be sent > in via SG_IO from userspace. > > A full workaround might be to break up such commands into sequences > of single DRQ ones, but that's just way too complex for something > that doesn't normally happen in real life. > > So, allow the attempt (it often works, despite the errata), > but log the event for reference when somebody screams. > > Signed-off-by: Mark Lord applied patches 1-2 > Tejun/Alan/Jeff: > > We may also want a patch to prevent libata-eh from downshifting > all the way to PIO on these chipsets, but I am not sure how to > accomplish that from inside sata_mv. Any suggestions? Do we really want that? Seems to me we need that for older bridged PATA devices attached to a SATA bridge. Jeff