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

Hi Simon,

CC DT

On Wed, Jul 12, 2017 at 7:49 AM, Simon Horman [off-list ref] wrote:

On Tue, Jul 11, 2017 at 07:59:31PM +0200, Geert Uytterhoeven wrote:

quoted

On Tue, Jul 11, 2017 at 2:38 PM, Simon Horman
[off-list ref] wrote:

quoted

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 <redacted>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

quoted

---
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.

That sounds good to me. But other people may disagree.
Oh, no CC to the devicetree folks. Fixed.
Patch at https://patchwork.kernel.org/patch/9834611/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds