From owner-svn-src-head@FreeBSD.ORG Mon Feb 9 18:33:31 2009 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 58C81106564A; Mon, 9 Feb 2009 18:33:31 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (bsdimp.com [199.45.160.85]) by mx1.freebsd.org (Postfix) with ESMTP id 0BD698FC12; Mon, 9 Feb 2009 18:33:30 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from localhost (localhost [127.0.0.1]) by harmony.bsdimp.com (8.14.2/8.14.1) with ESMTP id n19IUnxk027985; Mon, 9 Feb 2009 11:30:49 -0700 (MST) (envelope-from imp@bsdimp.com) Date: Mon, 09 Feb 2009 11:30:53 -0700 (MST) Message-Id: <20090209.113053.65361811.imp@bsdimp.com> To: xcllnt@mac.com From: "M. Warner Losh" In-Reply-To: <2EA5FEEB-E676-4D1B-9700-399C783F4590@mac.com> References: <94616FBD-4638-4C51-990C-06A943B1BA2A@mac.com> <200902090923.45887.jhb@freebsd.org> <2EA5FEEB-E676-4D1B-9700-399C783F4590@mac.com> X-Mailer: Mew version 5.2 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: svn-src-head@freebsd.org, scottl@samsco.org, src-committers@freebsd.org, svn-src-all@freebsd.org, jhb@freebsd.org Subject: Re: svn commit: r188350 - in head/sys: amd64/amd64 arm/arm dev/usb2/core i386/i386 ia64/ia64 sys X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Feb 2009 18:33:31 -0000 In message: <2EA5FEEB-E676-4D1B-9700-399C783F4590@mac.com> Marcel Moolenaar writes: : : On Feb 9, 2009, at 6:23 AM, John Baldwin wrote: : : > On Monday 09 February 2009 12:37:53 am Marcel Moolenaar wrote: : >> : >> On Feb 8, 2009, at 5:00 PM, Scott Long wrote: : >> : >>> Busdma allows you to request bouncing for realignment. : >> : >> How exactly? : > : > The 'align' parameter to bus_dma_tag_create(). If your hardware : > needs buffers : > to be aligned on a 4-byte boundary and you bus_dmamap_load() a buffer : > where 'addr % 4 != 0', then the buffer is bounced. Since by default : > the new : > buffer starts on a page boundary, it satifies the 'addr % 4'. : : But according to the man page, bounce buffering may not : be implemented or not be applicable to a platform. It : seems to me that you cannot depend on this side-effect : in a generic driver. Are you guys talking only in terms : of i386 or is this generally applicable? There's no bounce buffering on MIPS right now, for example... There likely should be, but it isn't there now. Warner