Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752994AbbG2Foc (ORCPT ); Wed, 29 Jul 2015 01:44:32 -0400 Received: from mailgw01.mediatek.com ([218.249.47.110]:37497 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751629AbbG2Foa (ORCPT ); Wed, 29 Jul 2015 01:44:30 -0400 X-Listener-Flag: 11101 Message-ID: <1438148491.25925.89.camel@mhfsdcap03> Subject: Re: [PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver From: Yong Wu To: Robin Murphy , Russell King - ARM Linux CC: 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 , Date: Wed, 29 Jul 2015 13:41:31 +0800 In-Reply-To: <55B6530A.9050903@arm.com> 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> <55B6530A.9050903@arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2381 Lines: 66 On Mon, 2015-07-27 at 16:49 +0100, Robin Murphy wrote: > 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... Hi Russell, Robin, From I see in arm-smmu-v3.c in v4.2-rc1, The flush_pgtable seems like this: //========== dma_addr_t dma_addr; dma_addr = dma_map_page(dev, ptr, size, DMA_TO_DEVICE); if (dma_mapping_error(dev, dma_addr)) dev_err(dev, "failed to flush pgtable at %p\n", ptr); else dma_unmap_page(dev, dma_addr, size, DMA_TO_DEVICE); //========== I will change map like this and use dma_map_single instead. Is this also seems to be not proper? Then how to do it? add this before unmap? : dma_sync_single_for_device(dev, dma_addr, size, DMA_TO_DEVICE); > > 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/