linux-kernel - Re: [RFC v5 net-next 01/13] mfd: ocelot: add support for external mfd control over SPI for the VSC7512

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Message-ID: <Yd3PPMOAcwRS6SlF@piout.net>
Date:   Tue, 11 Jan 2022 19:41:00 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Colin Foster <colin.foster@...advantage.com>
Cc:     Lee Jones <lee.jones@...aro.org>, Mark Brown <broonie@...nel.org>,
        linux-gpio@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Andrew Lunn <andrew@...n.ch>, UNGLinuxDriver@...rochip.com,
        Claudiu Manoil <claudiu.manoil@....com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [RFC v5 net-next 01/13] mfd: ocelot: add support for external
 mfd control over SPI for the VSC7512

On 11/01/2022 10:28:15-0800, Colin Foster wrote:
> 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.

Indeed, I guess at some point you'll need the irqchip driver too. Until
now, what I did was handling the irq controller inside the mfd driver as
reusing the irqchip driver is not trivial. Ths create a bit of code
duplication but it is not that bad.

> 
> 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

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com