From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v2 1/9] iommu/io-pgtable-arm: Allow appropriate DMA API use Date: Fri, 31 Jul 2015 12:22:27 +0100 Message-ID: <20150731112226.GB29497@arm.com> References: <6999933bfa9b3d50853fd023d455c837a0d7ff23.1438195011.git.robin.murphy@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <6999933bfa9b3d50853fd023d455c837a0d7ff23.1438195011.git.robin.murphy-5wv7dgnIgG8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Robin Murphy Cc: "laurent.pinchart+renesas-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org" , "linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: iommu@lists.linux-foundation.org Hi Robin, On Wed, Jul 29, 2015 at 07:46:04PM +0100, Robin Murphy wrote: > Currently, users of the LPAE page table code are (ab)using dma_map_page() > as a means to flush page table updates for non-coherent IOMMUs. Since > from the CPU's point of view, creating IOMMU page tables *is* passing > DMA buffers to a device (the IOMMU's page table walker), there's little > reason not to use the DMA API correctly. > > Allow IOMMU drivers to opt into DMA API operations for page table > allocation and updates by providing their appropriate device pointer. > The expectation is that an LPAE IOMMU should have a full view of system > memory, so use streaming mappings to avoid unnecessary pressure on > ZONE_DMA, and treat any DMA translation as a warning sign. > > Signed-off-by: Robin Murphy > --- > > Changes since v1[1]: > - Make device pointer mandatory and use DMA API unconditionally > - Remove flush_pgtable callback entirely > - Style, consistency and typo fixes I think this is looking good now, thanks. I'll add it to my ARM SMMU queue for 4.3. Will