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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 ABE00C46478 for ; Thu, 4 Jul 2019 08:20:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8307E218A4 for ; Thu, 4 Jul 2019 08:20:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727056AbfGDIUE (ORCPT ); Thu, 4 Jul 2019 04:20:04 -0400 Received: from 8bytes.org ([81.169.241.247]:34084 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725957AbfGDIUE (ORCPT ); Thu, 4 Jul 2019 04:20:04 -0400 Received: by theia.8bytes.org (Postfix, from userid 1000) id 49E032FB; Thu, 4 Jul 2019 10:20:03 +0200 (CEST) Date: Thu, 4 Jul 2019 10:20:01 +0200 From: Joerg Roedel To: Rob Clark Cc: iommu@lists.linux-foundation.org, dri-devel@lists.freedesktop.org, aarch64-laptops@lists.linaro.org, Jordan Crouse , Rob Clark , Greg Kroah-Hartman , "Rafael J. Wysocki" , Ulf Hansson , Rasmus Villemoes , Heikki Krogerus , Vivek Gautam , Bartosz Golaszewski , Joe Perches , Sudeep Holla , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] iommu: add support for drivers that manage iommu explicitly Message-ID: <20190704082001.GD6546@8bytes.org> References: <20190702202631.32148-1-robdclark@gmail.com> <20190702202631.32148-2-robdclark@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190702202631.32148-2-robdclark@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Rob, On Tue, Jul 02, 2019 at 01:26:18PM -0700, Rob Clark wrote: > 1) In some cases the bootloader takes the iommu out of bypass and > enables the display. This is in particular a problem on the aarch64 > laptops that exist these days, and modern snapdragon android devices. > (Older devices also enabled the display in bootloader but did not > take the iommu out of bypass.) Attaching a DMA or IDENTITY domain > while scanout is active, before the driver has a chance to intervene, > makes things go *boom* Just to make sure I get this right: The bootloader inializes the SMMU and creates non-identity mappings for the GPU? And when the SMMU driver in Linux takes over this breaks display output. > + /* > + * If driver is going to manage iommu directly, then avoid > + * attaching any non driver managed domain. There could > + * be already active dma underway (ie. scanout in case of > + * bootloader enabled display), and interfering with that > + * will make things go *boom* > + */ > + if ((domain->type != IOMMU_DOMAIN_UNMANAGED) && > + dev->driver && dev->driver->driver_manages_iommu) > + return 0; > + When the default domain is attached, there is usually no driver attached yet. I think this needs to be communicated by the firmware to Linux and the code should check against that. > - bool suppress_bind_attrs; /* disables bind/unbind via sysfs */ > + bool suppress_bind_attrs:1; /* disables bind/unbind via sysfs */ > + bool driver_manages_iommu:1; /* driver manages IOMMU explicitly */ How does this field get set? Joerg