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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 2711BC433E0 for ; Wed, 1 Jul 2020 19:31:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8BDD20760 for ; Wed, 1 Jul 2020 19:31:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="CvLLE1I/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726505AbgGATbb (ORCPT ); Wed, 1 Jul 2020 15:31:31 -0400 Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:8034 "EHLO hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725771AbgGATba (ORCPT ); Wed, 1 Jul 2020 15:31:30 -0400 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 01 Jul 2020 12:30:40 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Wed, 01 Jul 2020 12:31:30 -0700 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Wed, 01 Jul 2020 12:31:30 -0700 Received: from [10.26.73.166] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 1 Jul 2020 19:31:25 +0000 Subject: Re: [PATCH v8 2/3] dt-bindings: arm-smmu: Add binding for Tegra194 SMMU To: Krishna Reddy , Robin Murphy CC: "joro@8bytes.org" , "will@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Thierry Reding , "Yu-Huan Hsu" , Sachin Nikam , Pritesh Raithatha , Timo Alho , Bitan Biswas , Mikko Perttunen , Nicolin Chen , Bryan Huntsman , "nicoleotsuka@gmail.com" References: <20200630001051.12350-1-vdumpa@nvidia.com> <20200630001051.12350-3-vdumpa@nvidia.com> <3e655881-bac4-f083-44ed-cfa0a61298d0@arm.com> <0d4f46d6-6a4e-bca0-bcf3-0e22a950e57b@nvidia.com> From: Jon Hunter Message-ID: Date: Wed, 1 Jul 2020 20:31:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1593631840; bh=ZGC9lIP7pPgpxF+KbHUwdguRxLIBieIt7a3FT6LfKBE=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=CvLLE1I/rFJiMNetZpFnz4yrdJ2p2ysI4goElMGZaDmeIVvVfVkPcE6W+6+if3Sfy hgHM/wd7JR6WiVc/L/HA8spH+rxaX2jlJiDy/BEej5nmfxCUuyIeZTU23xMEzZa+gz HOGByhGzv3+Pz7ZCoHeWiT9zamCpZCj8ZaJ51zSIgFJzlXRr9XLOgnzvwkroR2XR2c P8AfxVYUtxDd1I1+oE1pR3gWEwJhDFEfEC/+xUo8pl6K1i42OiM/yeI7PvPJ8l7hz7 pgv9UdvRpVXBpNklXhs5oy5hBb3hr5wC1/MtI7j556F/XMpXMuqH8JyTP0SqvcNqjv xnRkIjOcIvwhw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/07/2020 20:00, Krishna Reddy wrote: >>>>> + items: >>>>> + - enum: >>>>> + - nvdia,tegra194-smmu >>>>> + - const: arm,mmu-500 >>> >>>> Is the fallback compatible appropriate here? If software treats this as a standard MMU-500 it will only program the first instance (because the second isn't presented as a separate MMU-500) - is there any way that isn't going to blow up? >>> >>> When compatible is set to both nvidia,tegra194-smmu and arm,mmu-500, implementation override ensure that both instances are programmed. Isn't it? I am not sure I follow your comment fully. > >> The problem is, if for some reason someone had a Tegra194, but only set the compatible string to 'arm,mmu-500' it would assume that it was a normal arm,mmu-500 and only one instance would be programmed. We always want at least 2 of the 3 instances >programmed and so we should only match 'nvidia,tegra194-smmu'. In fact, I think that we also need to update the arm_smmu_of_match table to add 'nvidia,tegra194-smmu' with the data set to &arm_mmu500. > > In that case, new binding "nvidia,smmu-v2" can be added with data set to &arm_mmu500 and enumeration would have nvidia,tegra194-smmu and another variant for next generation SoC in future. I think you would be better off with nvidia,smmu-500 as smmu-v2 appears to be something different. I see others have a smmu-v2 but I am not sure if that is legacy. We have an smmu-500 and so that would seem more appropriate. Jon -- nvpublic