Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935091AbaGROOF (ORCPT ); Fri, 18 Jul 2014 10:14:05 -0400 Received: from fw-tnat.austin.arm.com ([217.140.110.23]:42751 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934714AbaGROOC (ORCPT ); Fri, 18 Jul 2014 10:14:02 -0400 Date: Fri, 18 Jul 2014 15:13:35 +0100 From: Catalin Marinas To: Olof Johansson Cc: Laura Abbott , Will Deacon , David Riley , "linux-arm-kernel@lists.infradead.org" , Ritesh Harjain , linux-mm , "linux-kernel@vger.kernel.org" Subject: Re: [PATCHv4 3/5] common: dma-mapping: Introduce common remapping functions Message-ID: <20140718141335.GC4608@arm.com> References: <1404324218-4743-1-git-send-email-lauraa@codeaurora.org> <1404324218-4743-4-git-send-email-lauraa@codeaurora.org> 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) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 09, 2014 at 11:46:56PM +0100, Olof Johansson wrote: > On Wed, Jul 2, 2014 at 11:03 AM, Laura Abbott wrote: > > For architectures without coherent DMA, memory for DMA may > > need to be remapped with coherent attributes. Factor out > > the the remapping code from arm and put it in a > > common location to reduced code duplication. > > > > Signed-off-by: Laura Abbott > > Hm. The switch from ioremap to map_vm_area() here seems to imply that > lib/ioremap can/should be reworked to use just wrap the vmalloc > functions too? ioremap_page_range() does not require the allocation of a map page array and assumes that the mapped memory is physically contiguous. This would be more efficient than the vmap() implementation which is generic enough to allow non-contiguous memory allocations. At some point, we'll have to support SMMU on arm64 and we can have 4 combinations of coherency and IOMMU. When an IOMMU is present, we don't require physically contiguous memory but we may require non-cacheable mappings, in which case vmap comes in handy. -- 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/