From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933605AbXGZNAA (ORCPT ); Thu, 26 Jul 2007 09:00:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754028AbXGZM7w (ORCPT ); Thu, 26 Jul 2007 08:59:52 -0400 Received: from rv-out-0910.google.com ([209.85.198.188]:15292 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759018AbXGZM7v (ORCPT ); Thu, 26 Jul 2007 08:59:51 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=FR8WoilnbFyWi7GwWfWGSQX+hxMehcp2r+cmAIs05FM5ys1CxzHnkGBrPN54p0RQ1jUplSeBaZzC9kMGs4l/NuNmOKtllPxVd2AXcFRIySB2AgD4aTQObN7vrIk6PxIwcFHKHtqDXW1aok1lvC0+axAFwIYkP4kNhkyNxpWvoSE= Message-ID: <7e5f60720707260559m64211206q581a4c83c9060485@mail.gmail.com> Date: Thu, 26 Jul 2007 14:59:51 +0200 From: "Peter Bortas" To: "Marcus Comstedt" Subject: Re: [PATCH] Fix DMA on Dreamcast Cc: "Adrian McMenamin" , "Andrew Morton" , linux-kernel@vger.kernel.org, lethal@users.sourceforge.net In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <92a12cdb0707191230g216feaf2ied3e95bacf4dd572@mail.gmail.com> <20070720120408.1f190269.akpm@linux-foundation.org> <92a12cdb0707210322m6670acaer768d078c5e358b0c@mail.gmail.com> <7e5f60720707210424w48f9dc10hff044d702f7bd1d3@mail.gmail.com> <92a12cdb0707210506t5cf58cc4gc5b70f335545dc3f@mail.gmail.com> <7e5f60720707210713o4ff0825eu463abee77dc1f04c@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 7/26/07, Marcus Comstedt wrote: > > "Peter Bortas" writes: > > > On 7/21/07, Adrian McMenamin wrote: > >> On 21/07/07, Peter Bortas wrote: > >> > >> > > >> > Sidenote: Does Linux handle the Dreamcast DMA errata? > >> > > >> > >> You need to explain what you mean (at least to me!). > >> > >> If you mean will it degrade gracefully - not without this patch if set > >> to the (correct) defconfig. With iffy settings it will. > > > > If I remember correctly (and that's a big if since I last looked at it > > in 2001) some revisions of the Dreamcast hardware would sporadically > > lock up if you scheduled a new DMA request to quickly after a previous > > one, even if you checked the ready bit. It's worked around by a delay > > of X microseconds as recommended by Sega engineers. I don't remember > > the value of X, nor where exactly in the flow this workaround should > > be applied. > > > > Adding Marcus in case he has a better memory than me. > > > I don't remeber any such delay. Are you sure you're not thinking > about the G2 bus problem (where accesses need to be programatically > serialized, whether they are PIO or DMA)? In that case my memory is worse than I thought. I'll see if I can dig up my old notes. -- Peter Bortas