Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754113AbbG0Pth (ORCPT ); Mon, 27 Jul 2015 11:49:37 -0400 Received: from eu-smtp-delivery-143.mimecast.com ([146.101.78.143]:38505 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751756AbbG0Ptf convert rfc822-to-8bit (ORCPT ); Mon, 27 Jul 2015 11:49:35 -0400 Message-ID: <55B6530A.9050903@arm.com> Date: Mon, 27 Jul 2015 16:49:30 +0100 From: Robin Murphy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Russell King - ARM Linux CC: Yong Wu , Joerg Roedel , Thierry Reding , Mark Rutland , Matthias Brugger , "devicetree@vger.kernel.org" , "pebolle@tiscali.nl" , "arnd@arndb.de" , "srv_heupstream@mediatek.com" , Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" , Tomasz Figa , "iommu@lists.linux-foundation.org" , Rob Herring , Daniel Kurtz , Sasha Hauer , "cloud.chou@mediatek.com" , "linux-mediatek@lists.infradead.org" , "frederic.chen@mediatek.com" , "mitchelh@codeaurora.org" , "linux-arm-kernel@lists.infradead.org" , Lucas Stach Subject: Re: [PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver References: <1437037475-9065-1-git-send-email-yong.wu@mediatek.com> <1437037475-9065-6-git-send-email-yong.wu@mediatek.com> <55B630CE.4050803@arm.com> <20150727153148.GJ7557@n2100.arm.linux.org.uk> In-Reply-To: <20150727153148.GJ7557@n2100.arm.linux.org.uk> X-OriginalArrivalTime: 27 Jul 2015 15:49:31.0349 (UTC) FILETIME=[D3CDB850:01D0C883] X-MC-Unique: Kkuo4OQ0Tj6z8ky3cm-q_g-1 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1641 Lines: 40 On 27/07/15 16:31, Russell King - ARM Linux wrote: > On Mon, Jul 27, 2015 at 02:23:26PM +0100, Robin Murphy wrote: >> On 16/07/15 10:04, Yong Wu wrote: >>> This patch adds support for mediatek m4u (MultiMedia Memory Management >>> Unit). >>> >>> Signed-off-by: Yong Wu >> [...] >>> +static void mtk_iommu_flush_pgtable(void *ptr, size_t size, void *cookie) >>> +{ >>> + struct mtk_iommu_domain *domain = cookie; >>> + unsigned long offset = (unsigned long)ptr & ~PAGE_MASK; >>> + >>> + dma_map_page(domain->data->dev, virt_to_page(ptr), offset, >>> + size, DMA_TO_DEVICE); >> >> Nit: this looks like it may as well be dma_map_single. >> >> It would probably be worth following it with a matching unmap too, just to >> avoid any possible leakage bugs (especially if this M4U ever appears in a >> SoC supporting RAM above the 32-bit boundary). > > Why not do the job properly? Take a look at how I implemented the > streaming DMA API on Tegra SMMU (patch set recently sent out earlier > today). > > There's no need for hacks like dma_map_page() (and discarding it's > return value) or dma_map_page() followed by dma_unmap_page(). Indeed, as it happens I do have a branch where I prototyped that for the long-descriptor io-pgtable-arm code a while ago; this discussion has prompted me to dig it up again. Stay tuned, folks... Robin. -- 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/