From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937694AbXGUON3 (ORCPT ); Sat, 21 Jul 2007 10:13:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760448AbXGUONV (ORCPT ); Sat, 21 Jul 2007 10:13:21 -0400 Received: from py-out-1112.google.com ([64.233.166.178]:54201 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757619AbXGUONU (ORCPT ); Sat, 21 Jul 2007 10:13:20 -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=jqXhxg5FXvcc+3DszBsNpacqeA1klho3Zw2dkYAKxiHknC/dklYYahRdGAIMQw9mcmMMn4Aqz7RQvj4lUv2RxhwNH8vaml9tlTS1Z9sIPfJqmwvqvHGtZCOsfd/WtoZdC3Kms/dqlhm0DGpkEpUr32jra3sG5hKsK45G5/h9nyw= Message-ID: <7e5f60720707210713o4ff0825eu463abee77dc1f04c@mail.gmail.com> Date: Sat, 21 Jul 2007 16:13:19 +0200 From: "Peter Bortas" To: "Adrian McMenamin" Subject: Re: [PATCH] Fix DMA on Dreamcast Cc: "Andrew Morton" , linux-kernel@vger.kernel.org, lethal@users.sourceforge.net, marcus@mc.pp.se In-Reply-To: <92a12cdb0707210506t5cf58cc4gc5b70f335545dc3f@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Peter Bortas