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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 19874C6778F for ; Fri, 27 Jul 2018 09:03:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C65EC20671 for ; Fri, 27 Jul 2018 09:03:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C65EC20671 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730590AbeG0KYY (ORCPT ); Fri, 27 Jul 2018 06:24:24 -0400 Received: from foss.arm.com ([217.140.101.70]:39170 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729492AbeG0KYY (ORCPT ); Fri, 27 Jul 2018 06:24:24 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9A4A515AD; Fri, 27 Jul 2018 02:03:28 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6B3DE3F2EA; Fri, 27 Jul 2018 02:03:28 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id E42E41AE17A0; Fri, 27 Jul 2018 10:03:28 +0100 (BST) Date: Fri, 27 Jul 2018 10:03:28 +0100 From: Will Deacon To: Joerg Roedel Cc: Dmitry Osipenko , Greg Kroah-Hartman , "Rafael J. Wysocki" , Thierry Reding , Jonathan Hunter , Mikko Perttunen , Rob Herring , Frank Rowand , Ben Skeggs , Russell King , Catalin Marinas , Nicolas Chauvet , devicetree@vger.kernel.org, nouveau@lists.freedesktop.org, iommu@lists.linux-foundation.org, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v1 0/6] Resolve unwanted DMA backing with IOMMU Message-ID: <20180727090328.GH28088@arm.com> References: <20180726231624.21084-1-digetx@gmail.com> <20180727082512.lpvmeuvxnw3mpeym@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180727082512.lpvmeuvxnw3mpeym@8bytes.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 27, 2018 at 10:25:13AM +0200, Joerg Roedel wrote: > On Fri, Jul 27, 2018 at 02:16:18AM +0300, Dmitry Osipenko wrote: > > The proposed solution adds a new option to the base device driver > > structure that allows device drivers to explicitly convey to the drivers > > core that the implicit IOMMU backing for devices must not happen. > > Why is IOMMU mapping a problem for the Tegra GPU driver? > > If we add something like this then it should not be the choice of the > device driver, but of the user and/or the firmware. Agreed, and it would still need somebody to configure an identity domain so that transactions aren't aborted immediately. We currently allow the identity domain to be used by default via a command-line option, so I guess we'd need a way for firmware to request that on a per-device basis. Will