From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] libata: Add MMIO support to pata_sil680 Date: Sun, 27 May 2007 22:21:05 -0400 Message-ID: <465A3C91.7020002@garzik.org> References: <20070515061239.611A2DDEE9@ozlabs.org> <1179209697.32247.153.camel@localhost.localdomain> <20070523144217.5abd9fdf@the-village.bc.nu> <1179960518.32247.948.camel@localhost.localdomain> <20070524003123.77b9c81c@the-village.bc.nu> <1179963820.32247.996.camel@localhost.localdomain> <20070524001302.GA18571@devserv.devel.redhat.com> <1179978137.32247.1035.camel@localhost.localdomain> <20070524105407.64514929@the-village.bc.nu> <46556E5D.3070203@pobox.com> <20070524120915.40b594a8@the-village.bc.nu> <46562E03.3020503@garzik.org> <20070525014027.3feabe50@the-village.bc.nu> <4656330E.2000604@garzik.org> <20070525152028.05b79c83@the-village.bc.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:42742 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751725AbXE1CVJ (ORCPT ); Sun, 27 May 2007 22:21:09 -0400 In-Reply-To: <20070525152028.05b79c83@the-village.bc.nu> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: Benjamin Herrenschmidt , Linux IDE Alan Cox wrote: > Correct, but it is also extremely slow. No point discussing fast paths > for odd if() tests through the code when you burn 100nS unneccessarily > every time you issue a command via PIO is there. BTW if you wanna start PIO speed tuning, ISTR the device-select code does not cache selections. We always unconditionally select a device before a command in ata_qc_issue_prot(), IIRC. ISTR for some cases this was intentional (following ATADRVR) but I bet adding code to -not- select a device, if it is already selected, would speed things up on slow PATA machines. ata_qc_issue_prot() and ata_dev_select() would be starting points if you're interested. Jeff