linux-kernel - Re: [PATCH V2 4/5] dt-bindings: spi: spi-nxp-fspi: Add support for imx8mm, imx8qxp

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Date:   Tue, 11 Feb 2020 12:05:01 -0600
From:   Rob Herring <robh@...nel.org>
To:     Adam Ford <aford173@...il.com>
Cc:     linux-spi <linux-spi@...r.kernel.org>,
        Yogesh Gaur <yogeshgaur.83@...il.com>,
        Ashish Kumar <ashish.kumar@....com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2 4/5] dt-bindings: spi: spi-nxp-fspi: Add support for
 imx8mm, imx8qxp

On Tue, Feb 11, 2020 at 4:49 AM Adam Ford <aford173@...il.com> wrote:
>
> On Thu, Feb 6, 2020 at 2:46 PM Rob Herring <robh@...nel.org> wrote:
> >
> > On Sun, Feb 02, 2020 at 06:59:49AM -0600, Adam Ford wrote:
> > > Add support for nxp,imx8qxp-fspi and nxp,imx8mm-fspi do the bindings
> >
> > s/do/to/
>
> Oops.  Thanks for catching that.
>
> >
> > > document.
> > >
> > > Signed-off-by: Adam Ford <aford173@...il.com>
> > > ---
> > > V2: No change
> > >
> > > diff --git a/Documentation/devicetree/bindings/spi/spi-nxp-fspi.txt b/Documentation/devicetree/bindings/spi/spi-nxp-fspi.txt
> > > index 2cd67eb727d4..7ac60d9fe357 100644
> > > --- a/Documentation/devicetree/bindings/spi/spi-nxp-fspi.txt
> > > +++ b/Documentation/devicetree/bindings/spi/spi-nxp-fspi.txt
> > > @@ -2,6 +2,9 @@
> > >
> > >  Required properties:
> > >    - compatible : Should be "nxp,lx2160a-fspi"
> > > +                         "nxp,imx8qxp-fspi"
> > > +                         "nxp,imx8mm-fspi"
> >
> > All 3 are different and no compatibility?
>
> This was all based on a series from NXP's repo where they have some
> data tables all associated to the various compatible entries, and they
> created a place holder for quirks.  Based on an older NXP repo, it
> seems like there might be some quirks associated to the different
> families, but the newer repo where I got this patch series didn't
> implement them, however, it's possible the quirks may enhance
> functionality later. If that's true, I think this is the best solution
> for future enhancements without having to change the compatibility
> names down the road.  Maybe someone from NXP can comment?  I am just
> trying to help push things upstream so we can support QSPI flash.  I
> would prefer to keep them separate for now, because we might have
> these improvements later. However, I'll do what you request.  Do you
> want me to drop the additional compatible flags and just use the
> original, or create a new one that's a bit more generic?

Neither.

If you already know that they have differences, then as-is is fine.

If they are believed to be 'the same', then you do:

compatible = "nxp,imx8qxp-fspi", "nxp,imx8mm-fspi";

assuming i.MX8MM was the first version.

This allows a MX8QXP to work without OS changes if the driver already
supports the previous chip. And if any quirks are found, then the OS
can handle them without a DT change.

Rob