Re: [PATCH/RFC] gpio: rcar: add gen[123] fallback compatibility strings

[Simon Horman <horms@xxxxxxxxxxxx>]

On Tue, Jul 11, 2017 at 07:59:31PM +0200, Geert Uytterhoeven wrote:
> Hi Simon,
> 
> On Tue, Jul 11, 2017 at 2:38 PM, Simon Horman
> <horms+renesas@xxxxxxxxxxxx> wrote:
> > Add fallback compatibility string for R-Car Gen 1, 2 and 3.
> >
> > In the case of Renesas R-Car hardware we know that there are generations of
> > SoCs, f.e. Gen 1 and 2. But beyond that its not clear what the relationship
> > between IP blocks might be. For example, I believe that r8a7790 is older
> > than r8a7791 but that doesn't imply that the latter is a descendant of the
> > former or vice versa.
> >
> > We can, however, by examining the documentation and behaviour of the
> > hardware at run-time observe that the current driver implementation appears
> > to be compatible with the IP blocks on SoCs within a given generation.
> >
> > For the above reasons and convenience when enabling new SoCs a
> > per-generation fallback compatibility string scheme being adopted for
> > drivers for Renesas SoCs.
> >
> > Also deprecate renesas,gpio-rcar as its name is more generic than its
> > implementation.
> >
> > Signed-off-by: Simon Horman <horms+renesas@xxxxxxxxxxxx>
> 
> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> 
> > ---
> > Based on linux-gpio/for-next
> > ---
> >  .../devicetree/bindings/gpio/renesas,gpio-rcar.txt        | 15 +++++++++++----
> >  drivers/gpio/gpio-rcar.c                                  | 10 ++++++++++
> >  2 files changed, 21 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
> > index 6826a371fb69..48634b01f1bf 100644
> > --- a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
> > +++ b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
> > @@ -2,7 +2,7 @@
> >
> >  Required Properties:
> >
> > -  - compatible: should contain one of the following.
> > +  - compatible: should contain one or more of the following:
> >      - "renesas,gpio-r8a7743": for R8A7743 (RZ/G1M) compatible GPIO controller.
> >      - "renesas,gpio-r8a7778": for R8A7778 (R-Mobile M1) compatible GPIO controller.
> >      - "renesas,gpio-r8a7779": for R8A7779 (R-Car H1) compatible GPIO controller.
> > @@ -13,7 +13,14 @@ Required Properties:
> >      - "renesas,gpio-r8a7794": for R8A7794 (R-Car E2) compatible GPIO controller.
> >      - "renesas,gpio-r8a7795": for R8A7795 (R-Car H3) compatible GPIO controller.
> >      - "renesas,gpio-r8a7796": for R8A7796 (R-Car M3-W) compatible GPIO controller.
> > -    - "renesas,gpio-rcar": for generic R-Car GPIO controller.
> > +    - "renesas,rcar-gen1-gpio": for a generic R-Car Gen1 GPIO controller.
> > +    - "renesas,rcar-gen2-gpio": for a generic R-Car Gen2 or RZ/G1 GPIO controller.
> > +    - "renesas,rcar-gen3-gpio": for a generic R-Car Gen3 GPIO controller.
> > +    - "renesas,gpio-rcar": deprecated.
> > +
> > +    When compatible with the generic version nodes must list the
> > +    SoC-specific version corresponding to the platform first followed by
> > +    the generic version.
> 
> Besides for consistency, does it make sense to deprecate "renesas,gpio-rcar"
> (which means R-Car Gen1) and introduce "renesas,rcar-gen1-gpio"?
> It's not like new R-Car Gen1 SoCs will pop up anytime soon (do we want Linux
> support for R-Car E1?).

>From my PoV the only advantage of that portion of the change is improving
consistency. Perhaps it would be better to substitute it with something
like this:

	- "renesas,gpio-rcar": for a generic R-Car Gen1 GPIO controller.
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