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Miller" , Florian Fainelli , Vivien Didelot , Andrew Lunn , UNGLinuxDriver@microchip.com, Alexandre Belloni , Claudiu Manoil , Vladimir Oltean Subject: Re: [RFC v5 net-next 01/13] mfd: ocelot: add support for external mfd control over SPI for the VSC7512 Message-ID: <20220111182815.GC28004@COLIN-DESKTOP1.localdomain> References: <20211218214954.109755-1-colin.foster@in-advantage.com> <20211218214954.109755-2-colin.foster@in-advantage.com> <20211230014300.GA1347882@euler> <20220111003306.GA27854@COLIN-DESKTOP1.localdomain> <20220111165330.GA28004@COLIN-DESKTOP1.localdomain> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: MWHPR10CA0012.namprd10.prod.outlook.com (2603:10b6:301::22) To MWHPR1001MB2351.namprd10.prod.outlook.com (2603:10b6:301:35::37) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: ff4ac4bf-8fbd-417a-5f2e-08d9d5301525 X-MS-TrafficTypeDiagnostic: MWHPR10MB2032:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; 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And I think this can make sense and clean things up. The > > "ocelot_core" mfd will register every regmap range, regardless of > > whether any child actually uses them. Every child can then get regmaps > > by name, via dev_get_regmap. That'll get rid of the back-and-forth > > regmap hooks. > > I was under the impression that MFD would not always be used? > > Didn't you have a use-case where the child devices could be used > independently of anything else? > > If not, why don't you just register a single Regmap covering the whole > range? Then let the Regmap API deal with the concurrency handling. That's exactly the use-case I was considering. An example: "mscc,ocelot-miim" exists. It can currently be used in two different scenarios: directly with devicetree, or indirectly as in drivers/net/dsa/ocelot/seville_vsc9953.c mscc_miim_setup(dev, &bus, "VSC9953 internal MDIO bus", ocelot->targets[GCB], ocelot->map[GCB][GCB_MIIM_MII_STATUS & REG_MASK]); The "GCB_MIIM_MII_STATUS" parameter is the offset from the base for that regmap. See commit (b99658452355 "net: dsa: ocelot: felix: utilize shared mscc-miim driver for indirect…") (My apologies if the formatting of that commit refernece is incorrect) But in that case... the Seville driver makes a devcpu_gcb regmap located at 0x71070000. That regmap is created over the entire "GCB range". That gets passed into the mscc-miim driver, along with the base register location of the MIIM periperal. At the same time, mscc-miim can be probed independently, at which point it would create a smaller regmap at 0x7107009c (Documentation/devicetree/bindings/mscc-miim.txt) So the mscc-miim driver supports multiple use-cases. I expect the same type of "offset" idea can be reasonably added to the following drivers, all of which already exist but need to support the same type of use-case: mscc,ocelot-pinctrl, mscc,ocelot-sgpio, mscc,ocelot-miim, and mscc,vsc7514-serdes. As I'm bringing up different parts of the hardware, there might be more components that become necessary. With the exception of vsc7514-serdes, those all exist outside of MFD. The vsc7512-serdes driver currently relies on syscon / MFD, which adds a different complexity. One that I think probably merits a separate probe function. > > -- > Lee Jones [李琼斯] > Principal Technical Lead - Developer Services > Linaro.org │ Open source software for Arm SoCs > Follow Linaro: Facebook | Twitter | Blog