Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752194Ab3HBMOa (ORCPT ); Fri, 2 Aug 2013 08:14:30 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:33749 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751871Ab3HBMO3 (ORCPT ); Fri, 2 Aug 2013 08:14:29 -0400 Date: Fri, 2 Aug 2013 08:13:40 -0400 From: Konrad Rzeszutek Wilk To: Stefano Stabellini Cc: xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ian.Campbell@citrix.com, will.deacon@arm.com, linux@arm.linux.org.uk Subject: Re: [PATCH RFC 1/8] arm: make SWIOTLB available Message-ID: <20130802121340.GH24540@konrad-lan.dumpdata.com> References: <1375292732-7627-1-git-send-email-stefano.stabellini@eu.citrix.com> <334c4fe7-e40c-489c-84db-9bb58c705d44@email.android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2290 Lines: 59 On Fri, Aug 02, 2013 at 12:59:00PM +0100, Stefano Stabellini wrote: > On Wed, 31 Jul 2013, Konrad Rzeszutek Wilk wrote: > > Stefano Stabellini wrote: > > >Signed-off-by: Stefano Stabellini > > >CC: will.deacon@arm.com > > >CC: linux@arm.linux.org.uk > > >--- > > > arch/arm/Kconfig | 7 +++++++ > > > arch/arm/include/asm/dma-mapping.h | 24 ++++++++++++++++++++++++ > > > 2 files changed, 31 insertions(+), 0 deletions(-) > > > > > >diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > > >index ba412e0..05125ab 100644 > > >--- a/arch/arm/Kconfig > > >+++ b/arch/arm/Kconfig > > >@@ -1832,6 +1832,13 @@ config CC_STACKPROTECTOR > > > neutralized via a kernel panic. > > > This feature requires gcc version 4.2 or above. > > > > > >+config SWIOTLB > > >+ def_bool y > > >+ select NEED_SG_DMA_LENGTH > > >+ > > >+config IOMMU_HELPER > > >+ def_bool SWIOTLB > > >+ > > > > Could you explain the purpose of these two a bit more please? > > SWIOTLB is not available on arm at the moment. > We need to make it available, otherwise SWIOTLB_XEN won't be able to > select it. > > Similarly, IOMMU_HELPER is another lib Kconfig symbol needed by SWIOTLB > to compile. I was more curious about the NEED_SG_DMA_LENGTH and IOMMU_HELPER. I think the NEED_SG_DMA_LENGTH is optional? Or does SWIOTLB complain about? I do recall seeing a patch for this at some point but it was malformed. It was just changing SWIOTLB to use a macro for sg->dma_length or such. But the IOMMU_HELPER? That seems odds as the DMA API (which as you know is what SWIOTLB hooks up to) is _below_ the IOMMU API. Ah, it is 'iommu_is_span_boundary' function. Gotcha. Could you mention that in the git commit please? Just say that SWIOTLB uses some of the common code that IOMMU API uses - which is in the lib/iommu_helper.c hence the need for that. And for the NEED_SG_DMA_LENGTH let me dig up the patch at some point and send it your way so you can make it part of this series. -- 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/