From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934685Ab2DLUSt (ORCPT ); Thu, 12 Apr 2012 16:18:49 -0400 Received: from terminus.zytor.com ([198.137.202.10]:42760 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934651Ab2DLUSs (ORCPT ); Thu, 12 Apr 2012 16:18:48 -0400 Message-ID: <4F87388C.300@zytor.com> Date: Thu, 12 Apr 2012 13:18:20 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-Version: 1.0 To: Alessandro Rubini CC: mingo@elte.hu, akpm@linux-foundation.org, jbarnes@virtuousgeek.org, fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, giancarlo.asnaghi@st.com, alan@linux.intel.com Subject: Re: [PATCH V4 1/3] x86: introduce CONFIG_X86_DEV_DMA_OPS References: <4F87186B.9010303@zytor.com> <5965c5b1f828732b3599131fb21070aba6f1a386.1331622735.git.rubini@gnudd.com> <20120314065614.GB27480@elte.hu> <20120412201533.GA26533@mail.gnudd.com> In-Reply-To: <20120412201533.GA26533@mail.gnudd.com> X-Enigmail-Version: 1.4 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/2012 01:15 PM, Alessandro Rubini wrote: > > The current approach is using swiotlb and it works pretty well, though > with a limit of 4MB of swiotlb area. I've been considering use of the > DMA zone to this aim: internally I have some half-working thing that > resuses the ISA DMA zone for our own aims, raising the DMA limit to > 512MB. > > Do you think the approach may make sense? I use this basic > thing in Kconfig, to rely on GFP_DMA for the rest: > > config MAX_DMA_PADDR > int > default 536870912 if MAX_DMA_PADDR_512M > default 16777216 > > config MAX_DMA_PADDR_512M > bool > > (actually, we'd benefit from being able to use hex in defaults) > > Is this worth exploring, to possibly submit a patch in this direction? > Not as a compile-time patch. -hpa