Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964842AbcCOIX4 (ORCPT ); Tue, 15 Mar 2016 04:23:56 -0400 Received: from [198.137.202.9] ([198.137.202.9]:33439 "EHLO bombadil.infradead.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S933849AbcCOIXn (ORCPT ); Tue, 15 Mar 2016 04:23:43 -0400 Date: Tue, 15 Mar 2016 01:22:54 -0700 From: Christoph Hellwig To: Christoph Hellwig , Dan Williams , Vinod Koul , linux-renesas-soc@vger.kernel.org, "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "dmaengine@vger.kernel.org" , iommu@lists.linux-foundation.org, robin.murphy@arm.com, Laurent Pinchart , geert+renesas@glider.be, Linus Walleij , Arnd Bergmann , linux-arch@vger.kernel.org Subject: Re: [PATCH v5 3/9] dma-mapping: add dma_{map,unmap}_resource Message-ID: <20160315082254.GE9136@infradead.org> References: <1457404974-1800-1-git-send-email-niklas.soderlund+renesas@ragnatech.se> <1457404974-1800-4-git-send-email-niklas.soderlund+renesas@ragnatech.se> <20160308073847.GA15520@infradead.org> <20160310160522.GB1111@bigcity.dyn.berto.se> <20160311111522.GA3450@infradead.org> <20160311125846.GF1111@bigcity.dyn.berto.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160311125846.GF1111@bigcity.dyn.berto.se> User-Agent: Mutt/1.5.24 (2015-08-30) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 676 Lines: 12 On Fri, Mar 11, 2016 at 01:58:46PM +0100, Niklas S?derlund wrote: > Without an IOMMU this is easy since the phys_addr_t and dma_addr_t are > the same and no special care is needed. However if you have a IOMMU you > need to map the DMA slave phys_addr_t to a dma_addr_t using something > like this. Is it not very similar to dma_map_single() where one maps > processor virtual memory (instead if MMIO) so that it can be used with > DMA slaves? It's similar, but I don't think this actually works as a general case as there are quite a few places that expect to be able to have a struct page for a physical address. We'd at least need a very careful audit for that case.