From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: [PATCH 1/2] libata: switch to using block layer tagging support Date: Thu, 21 May 2009 09:44:05 -0400 Message-ID: <4A155AA5.3080704@rtr.ca> References: <20090520065942.GD11363@kernel.dk> <20090520070038.GE11363@kernel.dk> <1242845440.2881.74.camel@localhost.localdomain> <4A1452E9.7000204@garzik.org> <4A145458.5080302@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from rtr.ca ([76.10.145.34]:33366 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754887AbZEUNoG (ORCPT ); Thu, 21 May 2009 09:44:06 -0400 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Gwendal Grignou Cc: Jeff Garzik , James Bottomley , Grant Grundler , Jens Axboe , linux-ide@vger.kernel.org, htejun@gmail.com Gwendal Grignou wrote: > Jeff, you're right, I made some mistakes: > - Reading SiI3132 doc again, it only supports 32 command per port, so > the tags must be share among all the drives behind the same port. > But other chipset does support up to 128 commands per port. > - Jens' patch is working when all disks support NCQ. Only when we have > a mix of drives with or without NCQ we have a problem. .. Along those lines, the newer Marvell chipsets support up to 128 commands per host port. I seem to recall that the Pacific Digital Qstor chip can manage an insane number of commands -- something like 32 per device per PM port [eg. (15 * 32) in total per host port]. Seems to be a widespread kind of thing for non-legacy chipsets. Someday we really ought to beef up libata to allow host-chipset queuing of non-NCQ commands, too. Cheers