Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754494Ab3JBRIs (ORCPT ); Wed, 2 Oct 2013 13:08:48 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.21]:50658 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753987Ab3JBRIr (ORCPT ); Wed, 2 Oct 2013 13:08:47 -0400 Date: Wed, 2 Oct 2013 18:07:48 +0100 From: Catalin Marinas To: Stefano Stabellini Cc: Konrad Rzeszutek Wilk , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "Ian.Campbell@citrix.com" Subject: Re: [PATCH v6 10/19] xen: introduce xen_alloc/free_coherent_pages Message-ID: <20131002170747.GG29794@arm.com> References: <1380298207-29151-10-git-send-email-stefano.stabellini@eu.citrix.com> <20130930153143.GQ3106@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1685 Lines: 37 On Wed, Oct 02, 2013 at 06:03:46PM +0100, Stefano Stabellini wrote: > On Tue, 1 Oct 2013, Catalin Marinas wrote: > > On 30 Sep 2013, at 16:31, Konrad Rzeszutek Wilk wrote: > > > On Fri, Sep 27, 2013 at 05:09:58PM +0100, Stefano Stabellini wrote: > > >> xen_swiotlb_alloc_coherent needs to allocate a coherent buffer for cpu > > >> and devices. On native x86 and ARMv8 is sufficient to call > > >> __get_free_pages in order to get a coherent buffer, while on ARM we need > > >> to call the native dma_ops->alloc implementation. > > >> > > >> When arm64 stops using the swiotlb by default and starts having multiple > > >> dma_ops implementations, we'll use __get_dma_ops there too. > > > > > > I presume this is a future TODO, not some further patch (in which > > > case you should say in here the title of it). If it is a TODO could > > > you stick that in the sentence here somewhere to make it crytal clear that > > > it is not implemented. > > > > Thanks for pointing this out. The arm64 patch shouldn't be different > > from arm here. I thought a subsequent patch already added > > __get_dma_ops() for arm64. > > Yes, the arm64 patch already added __get_dma_ops. > > However I am not using __get_dma_ops to implement > xen_alloc_coherent_pages for arm64 because I can just use > __get_free_pages for the moment: So why do the work twice when we'll get coherency maintenance in the DMA ops? -- Catalin -- 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/