Re: [PATCH V8 1/2] mtd: spi-nor: Bindings for Cadence Quad SPI Flash Controller driver.

Marek Vasut
2016-02-01T21:13:46Z

On Monday, February 01, 2016 at 10:03:35 PM, Brian Norris wrote:
> On Wed, Jan 13, 2016 at 03:39:17AM +0100, Marek Vasut wrote:
> > On Wednesday, January 13, 2016 at 03:26:08 AM, Rob Herring wrote:
> > > On Mon, Jan 11, 2016 at 05:34:45AM +0100, Marek Vasut wrote:
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/mtd/cadence-quadspi.txt
> > > > @@ -0,0 +1,56 @@
> > > > +* Cadence Quad SPI controller
> > > > +
> > > > +Required properties:
> > > > +- compatible : Should be "cdns,qspi-nor".
> > >
> > > Fine, but I expect to see SOCs using this block add their own
> > > compatible strings. It wouldn't surprise me that we already have some
> > > using this block.
> > >
> > > Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> >
> > I finally got an Ack on this, I am so happy :-)
> >
> > As for the SoCs, there is Altera SoCFPGA Gen 5 and Gen 10 which uses
> > this. Then there is some TI SoC, but I don't know the model. Vignesh (on
> > CC) would. Then there is some ST SoC, but I have no idea what that's all
> > about, sorry.
> >
> > All these SoCs should be capable of tweaking the block to fit their needs
> > by just the DT properties. I believe they differ only in the FIFO depth
> > and sometimes someone is greedy and uses 4:16 CS multiplexer, which is
> > an external passive component, but that's all.
> >
> > Would we need soc-specific compatible strings if this is the case?
>
> It's nice when most things can be supported with a small set of DT
> properties, as you've done. But IUIC, I think it's usually good practice
> to define and use SoC-specific (or maybe SoC family) compatible strings
> in the docs and DTS files, in addition to the generic one, in case there
> are future quirks that need to be handled. Note that you don't actually
> have to use these in the driver yet, but it's good to have a definition.
> So you can, today, have:
>
> foo@xxxx {
> compatible = "ti,baz-12345", "cdns,qspi-nor";
> ...
> };
>
> And we have the option to pick up "ti,baz-12345" in the Linux driver *if
> needed.*

Ah, got it, thanks!

Best regards,
Marek Vasut