Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751580AbaJAJFX (ORCPT ); Wed, 1 Oct 2014 05:05:23 -0400 Received: from www.linutronix.de ([62.245.132.108]:36322 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750997AbaJAJFU (ORCPT ); Wed, 1 Oct 2014 05:05:20 -0400 Date: Wed, 1 Oct 2014 11:05:13 +0200 (CEST) From: Thomas Gleixner To: Peter Hurley cc: Akinobu Mita , LKML , Andrew Morton , Marek Szyprowski , Konrad Rzeszutek Wilk , David Woodhouse , Don Dutile , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , x86@kernel.org, iommu@lists.linux-foundation.org, Greg KH Subject: Re: [PATCH v3 0/5] enhance DMA CMA on x86 In-Reply-To: <542B5DC2.8020806@hurleysoftware.com> Message-ID: References: <1397567329-3771-1-git-send-email-akinobu.mita@gmail.com> <5426CA0A.7000806@hurleysoftware.com> <54294C0B.1060705@hurleysoftware.com> <542ABF77.1020402@hurleysoftware.com> <542B5DC2.8020806@hurleysoftware.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 30 Sep 2014, Peter Hurley wrote: > On 09/30/2014 07:45 PM, Thomas Gleixner wrote: > > Whether the proposed patchset is the correct solution to support it is > > a completely different question. > > This patchset has been in mainline since 3.16 and has already caused > regressions, so the question of whether this is the correct solution has > already been answered. Agreed. > > So either you stop this right now and help Akinobu to find the proper > > solution > > If this is only a test platform for ARM parts then I don't think it > unreasonable to suggest forking x86 swiotlb support into a iommu=cma > selector that gets DMA mapping working for this test platform and doesn't > cause a bunch of breakage. Breakage is not acceptable in any case. > Which is different than if the plan is to ship production units for x86; > then a general purpose solution will be required. > > As to the good design of a general purpose solution for allocating and > mapping huge order pages, you are certainly more qualified to help Akinobu > than I am. Fair enough. Still this does not make the case for outright rejecting the idea of supporting that kind of device even if it is a esoteric case. We deal with enough esoteric hardware in Linux and if done right, it's no harm to anyone. I'll have a look at the technical details. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/