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Miller" , Heiner Kallweit Subject: Re: [net-next PATCH v3 4/5] net: phy: Introduce fwnode_get_phy_id() Message-ID: <20200511055231.GA12725@lsv03152.swis.in-blr01.nxp.com> References: <20200505132905.10276-1-calvin.johnson@oss.nxp.com> <20200505132905.10276-5-calvin.johnson@oss.nxp.com> <67e263cf-5cd7-98d1-56ff-ebd9ac2265b6@arm.com> <83ab4ca4-9c34-4cdd-4413-3b4cdf96727d@arm.com> <20200508160755.GB10296@lsv03152.swis.in-blr01.nxp.com> <20200508181301.GF298574@lunn.ch> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200508181301.GF298574@lunn.ch> User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: SG2PR02CA0024.apcprd02.prod.outlook.com (2603:1096:3:17::36) To AM0PR04MB5636.eurprd04.prod.outlook.com (2603:10a6:208:130::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from lsv03152.swis.in-blr01.nxp.com (14.142.151.118) by SG2PR02CA0024.apcprd02.prod.outlook.com (2603:1096:3:17::36) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2979.27 via Frontend Transport; Mon, 11 May 2020 05:52:38 +0000 X-Originating-IP: [14.142.151.118] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: ebbe73b6-c677-4aed-ba4a-08d7f56f868f X-MS-TrafficTypeDiagnostic: AM0PR04MB7092:|AM0PR04MB7092: X-MS-Exchange-SharedMailbox-RoutingAgent-Processed: True X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-Forefront-PRVS: 04004D94E2 X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:AM0PR04MB5636.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(4636009)(346002)(376002)(39860400002)(366004)(136003)(396003)(33430700001)(52116002)(7696005)(186003)(6506007)(8676002)(1076003)(55236004)(26005)(5660300002)(54906003)(6916009)(316002)(478600001)(16526019)(6666004)(1006002)(7416002)(33440700001)(956004)(9686003)(55016002)(4326008)(8936002)(2906002)(86362001)(66946007)(66476007)(66556008)(33656002)(44832011)(110426005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: 9olgPWxzcgIiPW7+zZNopXx7i3DH9Xlra+1K+3LLpg5sKUPw8NrQjdEiNQ7uFG5Itdw+sOEKBtja+8RJaQqVHMtHjE0m420RjF4+5/PkW/6ljBoPWOSM4Wg+FOK8b3de07UkoSURoV4AWiFU4HCJ12mnGXJPabMYHtTKGk1z+DzOqD41G92Fxrpz3UVWKYJHhhO2cjcxeALVCnv6KWQDUhjwidDSxFSZH80xyKHFA9w8iFxSLqwdjyYLxcJMOnUmXtOPdF0f89PsXx9lWlxP+vkvP7pfRova/h+VIt/KtsdGWCQx9FprvDk/949pH+VBKYqt+RpRz9IlUOkLZVidAGgF7asAYeoK7udOcdmQyBtvYBGk1eKN3HOHdHg32QgkL8GuFNsQlttyVLL1R3PwJqbnE7pmKrjAVWcduuQNJZAT4N0LS5ZTbZm/Y/PcrSraOiPzb9g7ohUdaeCObUwX5HX4EN13FffG13ozPYWkTqk= X-OriginatorOrg: oss.nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: ebbe73b6-c677-4aed-ba4a-08d7f56f868f X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 May 2020 05:52:44.7823 (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: SHcjI5csWW4vhgRhFHhlutmYVvbIbXA/zKxFun/bGMBXtZfx8fELGz5dk6F43/sS1yMOkqAHcKoEBF1kUeSOwg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM0PR04MB7092 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks Andrew and Jeremy for the detailed discussion! On Fri, May 08, 2020 at 08:13:01PM +0200, Andrew Lunn wrote: > > > It does have a numeric version defined for EISA types. OTOH I suspect that > > > your right. If there were a "PHY\VEN_IDvvvv&ID_DDDD" definition, it may not > > > be ideal to parse it. Instead the normal ACPI model of exactly matching the > > > complete string in the phy driver might be more appropriate. > > > > IMO, it should be fine to parse the string to extract the phy_id. Is there any > > reason why we cannot do this? > > Some background here, about what the PHY core does. > > PHYs have two ID registers. This contains vendor, device, and often > revision of the PHY. Only the vendor part is standardised, vendors can > decide how to use the device part, but it is common for the lowest > nibble to be revision. The core will read these ID registers, and then > go through all the PHY drivers registered and ask them if they support > this ID. The drivers provide a table of IDs and masks. The mask is > applied, and then if the ID matches, the driver is used. The mask > allows the revision to be ignored, etc. > > There is a very small number of devices where the vendor messed up, > and did not put valid contents in the ID registers. In such cases, we > can read the IDs from device tree. These are then used in exactly the > same way as if they were read from the device. > > If you want the ACPI model to be used, an exact match on the string, > you are going to have to modify the core and the drivers. They > currently don't have any string, and have no idea about different > revisions which are out in the wild. I don't think ACPI mandates that OS driver use exact string match and not parse the string. First of all, I would suggest that we use "compatible" property instead of _CID. Not sure of a reason why we cannot. This will simplify implementation of fwnode APIs. Already I've pointed out couple of ASL files in tianocore where they are already used. one eg:https://github.com/tianocore/edk2-platforms/blob/master/Silicon/Marvell/Armada7k8k/AcpiTables/Armada80x0McBin/Dsdt.asl#L280 Even if we use _CID, I'm not sure we are prohibited from extracting characters (phy_id) from it. If we decide to use _CID, then we need to define somewhere and standardize exactly how we are going to use it. I'm not sure where we can do this. > > > > Similarly to how I suspect the next patch's use of "compatible" isn't ideal > > > either, because whether a device is c45 or not, should tend to be fixed to a > > > particular vendor/device implementation and not a firmware provided > > > property. > > Not exactly true. It is the combination of can the bus master do C45 > and can the device do C45. Unfortunately, we have no knowledge of the > bus masters capabilities, if it can do C45. And many MDIO drivers will > do a C22 transaction when asked to perform a C45 transaction. All new > submissions for MDIO drivers i ask for EOPNOTSUPP to be returned if > C45 is not supported. But we cannot rely on that. Too much history. Makes sense to me. > > > > I tend to agree with you on this. Even for DT, ideal case, IMO should be: > > > > 1) mdiobus_scan scans the mdiobus for c22 devices by reading phy id from > > registers 2 and 3 > > 2) if not found scan for c45 devices <= looks like this is missing in Linux > > 3) look for phy_id from compatible string. > > It is somewhat more complex, in that there are a small number of > devices which will respond to both C22 and C45. Generally, you want to > use C45 if supported. So you would want to do the C45 scan first. But > then the earlier problem comes to play, you have no idea if the bus > master actually correctly supports C45. > > Given the issues, we assume all bus masters and PHY devices are C22 > unless DT says the bus master and PHY combination is compatible with > C45. Makes sense to me.