Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 5 Jan 2023 14:04:47 +0200
From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     devicetree@vger.kernel.org, iommu@lists.linux.dev,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        linux-kernel@vger.kernel.org, Michael Walle <michael@walle.cc>
Subject: Re: [RFC PATCH] arm64: dts: ls1028a: mark ARM SMMU as DMA coherent
Message-ID: <20230105120447.vnr24pusr3ihdhwk@skbuf>
References: <20221208151514.3840720-1-vladimir.oltean@nxp.com>
 <2a188b8a-ab16-d5d4-ed5f-f8eec236e4ca@arm.com>
 <20221214165356.6tbzmfyoifqt4cwk@skbuf>
 <3f3112e4-65ff-105d-8cd7-60495ec9054a@arm.com>
 <20221219121618.z3dcyob542cnmdnk@skbuf>
 <67ae3a53-3db9-c1bc-2b67-08df14bc15cc@arm.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <67ae3a53-3db9-c1bc-2b67-08df14bc15cc@arm.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?6OVnJO3zIu13zZUc4WQSb9zW4C7NrecTDqjUfVC10hAYqsR6sf2Jz+OdcBxp?=
 =?us-ascii?Q?fNFkBD4XkusJNeGumph5yglATz2+5jPXOuA7BWoJLdQpRslS9//ixnHQPsiq?=
 =?us-ascii?Q?z4NHEPZ1wWcaA4CWwpnK5iS9uhKKLBE1QfRbxe02TQIthTu07GCMWxZVMiZz?=
 =?us-ascii?Q?vSb385ApGQrGoY6I6rmJjznmY4TZBMbFyviYrYLy40Aafxk4HJYcADk/YIjl?=
 =?us-ascii?Q?D+bn5kjqlzZJRmOzVJxmeHCwnh6w4+kqMO1cSdY48kYs+CPc7gUz+TgA7fVx?=
 =?us-ascii?Q?IJAPxYYRtcHwX9ENkpPuvHG6KGXnldLDxao2fcp7Db50tkrnG8YEymxQVi3j?=
 =?us-ascii?Q?TyYDsRzPLVaPQ1ErB1weP9IF+qk2Ii2cQGI/GmN3r/QODBIX89NeylJuN4bC?=
 =?us-ascii?Q?nVz+XqFEkyDD823REFxnlfkucF43LMFcc3rb6ZrKst+feIjHaPnwn9f4mKdQ?=
 =?us-ascii?Q?w7fM7zptVDJoxVgFA06wsEDOr9yYh8KnMj/DoF5j5l0cZvc0PPy6kEsS/nKe?=
 =?us-ascii?Q?VbMNWiDEwm0/yTEZgwwynSz1Cx2outD2MOQSao48oXd4LTmADHwjQTy633s5?=
 =?us-ascii?Q?PkyWRDtGwW3AvkZaHVtNTrAEmqFtE2BLI4repMStAKevjk9tMe9KrrmY/Xq2?=
 =?us-ascii?Q?jcdK03jReeBA76R+VeHuUl57UIZFhcQeXdkqDWHPn+82CytXma8KquwCJKwh?=
 =?us-ascii?Q?yNg3/g7Gt9/TYiiP93MWr9QhsGLZu8kZWAJqBch4N/ZHYE2xVzzT37R4cNZr?=
 =?us-ascii?Q?djTDN1ILo7B3jPuhg50XuTF0Wr/Udp5QQOZw+UlOdDG+zcs36dmmEbDP4N/E?=
 =?us-ascii?Q?6hszuzV1ja8Xd3GITsvpLY9upPRrvTKf22y+nDu2aftdys9H9x+xVjCVLQoQ?=
 =?us-ascii?Q?nhdBg95TwT04bsYQBY9D1Usc2Ubaehi4tMr3gX8eGaGbU1qpjTswN/3tyIVd?=
 =?us-ascii?Q?Ekndibo9io5Nnf8pMHpB/KnMQcmndrLea6CFO7k9gVXsBA9OWuu/gKl3C8Et?=
 =?us-ascii?Q?tr2eSWH1EMrD5uUymhVxhB2IkX29abeqrAiPo68Ok/rj1/5rT+b0QC1GpzXY?=
 =?us-ascii?Q?pfs6zU/rJXWG9qV0m2gYibsmf+N+ctkDR9JC8zIB5g61e7yEKuTsyZSPgf6S?=
 =?us-ascii?Q?1R7Ga0zHUyktEm7qfIyuo7UHkFcmuxwvHTVJVd2n53nzR8QsNtlwylmGohjg?=
 =?us-ascii?Q?cUIN5iM2ba4ouWUD7Y5loPexuEigziRqvp1Rm8NGCUb5X/PWMZUnWTaeoNko?=
 =?us-ascii?Q?ThJyWOJbyW7WgHLdPRSWWKOF6PnjcuiLrhxDXeNZIGGgTues+8sDxfo1QVxP?=
 =?us-ascii?Q?Ouxj6v8Xam7+jyP5RRKv5VsoLsxOHyvlv2WTYzAbeHeZR8dJRUARBYOaA7kC?=
 =?us-ascii?Q?f+DK3uhGqgXcXq8C7+mhyj2tSqEFp2PWdThmgY6HtOoORIuIcnSmwnK9YXCL?=
 =?us-ascii?Q?GaR6XIOOLJ9cEezdcLvHgY/pgin9xI4lqsEOK6Fk3uQiqOt4PyK7ebLyAs2/?=
 =?us-ascii?Q?OsgI7jCygKPduAYYuIuB/AhMQ+wQZhQLnIh0v9cSWOraYeHNLaxpUc5gZTpq?=
 =?us-ascii?Q?JAbc8qfWXKQIy/UMw7TB/pwVetjQv942gHp2uYzyDDEcnHuxNnlWk1s8/4QB?=
 =?us-ascii?Q?Rw=3D=3D?=
X-OriginatorOrg: nxp.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 1faea793-9620-4cfe-b105-08daef150c92
X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jan 2023 12:04:51.2825
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: YNxOQYK7qfNg5HGfSsBg8U62w4FywOFMzFXFPJzPGK9op5TokdKMK9Ynpp3LvdnJPPmjahoUVPPakz676ehGVQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM7PR04MB7032
X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,
        RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_PASS autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jan 03, 2023 at 06:12:29PM +0000, Robin Murphy wrote:
> > I have a side question, why is the dev_name() of your SMMU set to
> > "arm-smmu.0.auto" (determined by PLATFORM_DEVID_AUTO if I'm not mistaken)?
> 
> This is an ACPI-based machine, where platform device discovery and creation
> is... different :)
> 
> SMMUs are among those managed by drivers/acpi/arm64/iort.c
> 
> > I'm asking because I would like to study the mechanism through which
> > your SMMU platform device get probed, to make sure that it's not
> > possible, during shutdown, for both platform_driver :: shutdown()
> > and platform_driver :: remove() methods to get called by the driver core.
> > This is generally not disallowed, and even possible if the entity who
> > registers these platform devices has its ->shutdown() method pointing
> > at ->remove().
> 
> Yikes, I'd very much hope that that's not a thing!

Ah, ok. Appears to be fine. Looking at drivers/acpi/arm64/iort.c,
it seems that no one is removing those platform devices.