From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [RFC] AHCI Command Completion Coalescing(CCC) proposal Date: Fri, 9 Jun 2006 13:49:16 +0200 Message-ID: <20060609114916.GF31913@suse.de> References: <1149751860.29552.79.camel@forrest26.sh.intel.com> <44883BAE.7070406@pobox.com> <1149820043.5721.7.camel@forrest26.sh.intel.com> <4488EB4A.4050501@pobox.com> <4488EE69.7050907@gmail.com> <4488EF64.9070602@gmail.com> <1149825065.5721.22.camel@forrest26.sh.intel.com> <44890602.90002@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:4638 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S965241AbWFILtg (ORCPT ); Fri, 9 Jun 2006 07:49:36 -0400 Content-Disposition: inline In-Reply-To: <44890602.90002@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: "zhao, forrest" , Jeff Garzik , linux-ide@vger.kernel.org On Fri, Jun 09 2006, Tejun Heo wrote: > zhao, forrest wrote: > >On Fri, 2006-06-09 at 12:47 +0900, Tejun Heo wrote: > >>If we're gonna do it. EH needs only a few changes probably during > >>autopsy and report. Fixing up command issue path and implementing > >>command exclusion (NCQ vs. non-NCQ, sil24 does it in hardware, ahci > >>doesn't) will be a bit complex though. > > > >Would you please elaborate on command exclusion? Why NCQ commands need > >to be excluded from non-NCQ commands? > > AHCI spec rev 1.1, sect 1.7. The last paragraph says. > > "This multiple-use of the command list is achieved by the HBA only > moving its command list pointer when the BSY, DRQ, and ERR bits are > cleared by the device. System software is responsible to ensure that > queued and non-queued commands are not mixed in the command list." This, btw, was also the case with the legacy TCQ. -- Jens Axboe