linux-kernel - Re: [PATCH v2 3/4] dt-bindings: can: renesas,rcar-canfd: Document RZ/T2H and RZ/N2H SoCs

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Message-ID: <CA+V-a8tbvJvqnrMaY9UA3tf2CcfcyiRFZLgdy7S411=ZUCcQww@mail.gmail.com>
Date: Thu, 8 Jan 2026 19:25:18 +0000
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Marc Kleine-Budde <mkl@...gutronix.de>, Vincent Mailhol <mailhol@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Biju Das <biju.das.jz@...renesas.com>, linux-can@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 3/4] dt-bindings: can: renesas,rcar-canfd: Document
 RZ/T2H and RZ/N2H SoCs

Hi Krzysztof,

On Wed, Jan 7, 2026 at 8:28 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 06/01/2026 18:26, Lad, Prabhakar wrote:
> > Hi Krzysztof,
> >
> > Thank you for the review.
> >
> > On Fri, Jan 2, 2026 at 11:20 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> >>
> >> On Tue, Dec 30, 2025 at 11:58:13AM +0000, Prabhakar wrote:
> >>> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >>>
> >>> Document the CAN-FD controller used on the RZ/T2H and RZ/N2H SoCs. The
> >>> CAN-FD IP is largely compatible with the R-Car Gen4 block, but differs
> >>> in that AFLPN and CFTML are different, there is no reset line for the IP,
> >>> and it only supports two channels.
> >>>
> >>> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >>> ---
> >>> v1->v2:
> >>> - No changes made.
> >>> ---
> >>>  .../bindings/net/can/renesas,rcar-canfd.yaml  | 26 ++++++++++++++++++-
> >>>  1 file changed, 25 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml b/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
> >>> index fb709cfd26d7..4a83e9e34d67 100644
> >>> --- a/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
> >>> +++ b/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
> >>> @@ -50,6 +50,12 @@ properties:
> >>>                - renesas,r9a09g057-canfd     # RZ/V2H(P)
> >>>            - const: renesas,r9a09g047-canfd
> >>>
> >>> +      - const: renesas,r9a09g077-canfd      # RZ/T2H
> >>
> >>
> >> That's part of other enum with single compatibles.
> >>
> > There is no enum with single compatibles as of in next [0], there is
> > only one compatible `renesas,r9a09g047-canfd`. I can club this with
> > RZ/T2H one.
>
> This is the one which is supposed to be enum.
>
Ok.

> >
> > [0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml?h=next-20260106
> >
> >>> +
> >>> +      - items:
> >>> +          - const: renesas,r9a09g087-canfd  # RZ/N2H
> >>> +          - const: renesas,r9a09g077-canfd
> >>> +
> >>>    reg:
> >>>      maxItems: 1
> >>>
> >>> @@ -179,7 +185,6 @@ required:
> >>>    - clocks
> >>>    - clock-names
> >>>    - power-domains
> >>> -  - resets
> >>>    - assigned-clocks
> >>>    - assigned-clock-rates
> >>>    - channel0
> >>> @@ -243,11 +248,30 @@ allOf:
> >>>            minItems: 2
> >>>            maxItems: 2
> >>>
> >>> +  - if:
> >>> +      properties:
> >>> +        compatible:
> >>> +          contains:
> >>> +            const: renesas,r9a09g077-canfd
> >>> +    then:
> >>> +      properties:
> >>> +        interrupts:
> >>> +          maxItems: 8
> >>> +
> >>> +        interrupt-names:
> >>> +          maxItems: 8
> >>> +
> >>> +        resets: false
> >>> +    else:
> >>> +      required:
> >>> +        - resets
> >>
> >> Why is this de-synced with reset-names? Properties are supposed to
> >> behave the same way, not once requiring resets other time requiring
> >> reset-names.
> >>
> > There are SoCs that have a single reset and others that require two
> > resets. For SoCs that require two resets, the reset-names property is
> > marked as required, while for SoCs with a single reset it is not.
>
> Sure, but I asked why? We expect (and it is documented already in the
> docs) that xxx-names always follows xxx, so I really do not understand
> why reset-names are valid but resets are not.
>
Sorry for being clear earlier, it's already taken care in patch 1/4
[1] with the below hunk which will restrict RZ/T2H to not allow
reset-names.

+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - renesas,r9a09g047-canfd
+              - renesas,rzg2l-canfd
+    then:
+      required:
+        - reset-names
+    else:
+      properties:
+        reset-names: false


[1] https://lore.kernel.org/all/20251230115814.53536-2-prabhakar.mahadev-lad.rj@bp.renesas.com/

Cheers,
Prabhakar