From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 518E3C07E95 for ; Fri, 16 Jul 2021 06:27:19 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1DD0E613E7 for ; Fri, 16 Jul 2021 06:27:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DD0E613E7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7nFEFEp/Ibt4ojlOuapLtEwwuDzuN1fGe1/RqhLnIxc=; b=lx9P7sJndwtewq CJUXtlmXB2vvSzqbUzogsg2MdVaqa84cUQI7S4IIt6lEoGhTtyDtGfzx7xLZwY0G4p1W0yODGSIqy dQbpi0Lu4nOI5PU2Lp8B/7mqRES+zFRnS8slVpyoIEjKYCSJ87/jhdTVSRKS7rm1L4lYfyabuA/Qv 9sOEeazk9ouHX1Vtj973+l5s2vA9L4qCji6VB7oNf3r3gODAonmnIqjww2t4VqF0l3mxqf1zTyT7I nwXU4ttqNdNdw4EElBoFgMoM4L9BT0nrq7/LNwPYmbKjTmQS1d3JxErjQCtq+zpzhPUWPG5wk9DYU G/n03RsCObBh6OERfXsA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m4HHj-003L6E-Rk; Fri, 16 Jul 2021 06:25:19 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1m4HHh-003L65-GY for linux-arm-kernel@bombadil.infradead.org; Fri, 16 Jul 2021 06:25:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nUjvHWwQzpb8v3JLLhXC0gHnxeaBdGyJCLTEJYo+tDU=; b=huSKh0okN6XoYJ0y+dNAPgyNBm F7FXsLDRcvDHuySrVPIHVbyStwyItZ/mdSW3L/fqeJJ47c6kBdo/N6Poo2g0iLZB8JaYtHz8Pz2FR aF0dgTJomsYvCIKwL6zIjvxUHCQZVJ8bhRZeAG44PSQ4CKcVEXxGf6aM4lt8rptgyJLFsw3ryiGSE 231k4bokw+Cu6nOyqGfOabFJNNlO6dr/gzmeQIwo5Yqcsx4WM/Nj2H1DHuNNlJVHayhmrjC+8KUyb dstirsS0SKabaihWxuTE6mv8KdQ0UMLkuM7hdYgi4xIsWblap+VguVBQB6wwRahw5mGKn3GUSlZeH 07nz0j9w==; Received: from hch by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m4HGV-004DCm-CL; Fri, 16 Jul 2021 06:24:28 +0000 Date: Fri, 16 Jul 2021 07:24:03 +0100 From: Christoph Hellwig To: Robin Murphy Cc: Sven Peter , Will Deacon , Joerg Roedel , Arnd Bergmann , devicetree@vger.kernel.org, Hector Martin , linux-kernel@vger.kernel.org, Marc Zyngier , Mohamed Mediouni , Stan Skowronek , linux-arm-kernel@lists.infradead.org, Mark Kettenis , iommu@lists.linux-foundation.org, Alexander Graf , Alyssa Rosenzweig , Rob Herring , r.czerwinski@pengutronix.de, Mauro Carvalho Chehab , linux-media@vger.kernel.org Subject: Re: [PATCH v4 0/3] Apple M1 DART IOMMU driver Message-ID: References: <20210627143405.77298-1-sven@svenpeter.dev> <7261df01-34a9-4e53-37cd-ae1aa15b1fb4@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7261df01-34a9-4e53-37cd-ae1aa15b1fb4@arm.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 14, 2021 at 07:19:50PM +0100, Robin Murphy wrote: > Even at the DMA API level you could hide *some* of it (at the cost of > effectively only having 1/4 of the usable address space), but there are > still cases like where v4l2 has a hard requirement that a page-aligned > scatterlist can be mapped into a contiguous region of DMA addresses. Where does v4l2 make that broken assumption? Plenty of dma mapping implementations including dma-direct do not support that. Drivers need to call dma_get_merge_boundary() to check for that kind of behavior. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel