From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: ahci, SActive flag, and the HD activity LED Date: Tue, 2 Aug 2005 18:35:21 +0200 Message-ID: <20050802163519.GB3710@suse.de> References: <42EF93F8.8050601@fujitsu-siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:61573 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261588AbVHBQdw (ORCPT ); Tue, 2 Aug 2005 12:33:52 -0400 Content-Disposition: inline In-Reply-To: <42EF93F8.8050601@fujitsu-siemens.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Martin Wilck Cc: linux-kernel@vger.kernel.org, Jeff Garzik , linux-ide@vger.kernel.org, "Wichert, Gerhard" On Tue, Aug 02 2005, Martin Wilck wrote: > Hello Jeff, hello Jens, hello everybody, > > I am referring to the debate about whether or not setting the SActive > bit for non-NCQ ATA commands (e.g. http://lkml.org/lkml/2005/5/26/142). > > In our machines, this behavior of the Linux AHCI driver causes the HD > activity LED to stay on all the time. If I apply the attached trivial > patch (this is for the RedHat EL4.0-U1 kernel), the LED behaves nicely. > > Jeff has stated in the above thread that "SActive is intentionally used > for non-NCQ devices". However I find clear indication in the specs that > the SActive flag should be set if and only if tagged queuing is being > used, and only for a specified subset of commands that support queuing > (http://www.t13.org/docs2005/D1699r1e-ATA8-ACS.pdf, secs. 4.19 and > 4.20). The current mainline driver doesn't use queuing. > > If I am reading the specs correctly, that'd mean the ahci driver is > wrong in setting the SActive bit. Could you please comment? Jeff, in > particular, could you please give more detail why you say this flag is > "intentionally used"? I completely agree, that was my reading of the spec as well and hence my original posts about this in the NCQ thread. -- Jens Axboe