Re: [PATCH v4 1/7] dt-bindings: can: renesas,rcar-canfd: Document RZ/G3S SoC

[Claudiu Beznea <claudiu.beznea@tuxon.dev>]

Hi, Biju,

On 10/19/26 10:24, Biju Das wrote:
> Hi Claudiu,
> 
>> -----Original Message-----
>> From: Marc Kleine-Budde <mkl@pengutronix.de>
>> Sent: 16 October 2026 14:34
>> Subject: Re: [PATCH v4 1/7] dt-bindings: can: renesas,rcar-canfd: Document RZ/G3S SoC
>>
>> On 02.09.2026 17:15:38, Claudiu Beznea wrote:
>>> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>>
>>> The CAN FD controller found on the Renesas RZ/G3S SoC is largely
>>> compatible with the variant present on the RZ/G3E SoC. The main differences are:
>>> - the RZ/G3S provides only two CAN FD channels
>>> - the RZ/G3S supports only CAN FD operation; the Channel n CAN FD
>>>    Configuration Register does not implement the bits used to select
>>>    classical CAN-only mode (bit 30) or CAN FD-only mode (bit 28);
>>>    consequently, bit 31 (CAN FD Frame Distinction Enable) of the same
>>>    register is also not implemented
>>> - some bits in several registers (mainly reserved or status bits) are
>>>    read-write on the RZ/G3S but read-only on the RZ/G3E; their behavior is
>>>    otherwise identical: the bits read back as 0 on both SoCs and software
>>>    is allowed to write only 0 to them on the RZ/G3S
>>> - the RZ/G3S provides 256 acceptance filters, compared to 768 on the
>>>    RZ/G3E
>>> - the RZ/G3S can use PCLK clock as the CAN FD clock source through an
>>>    internal clock divider, while also supporting an external CAN FD clock
>>>    source
>>>
>>> Since:
>>> - the SoC clock generator provides to the CAN IP only the peripheral and
>>>    the RAM clocks
>>> - when sourced from the peripheral clock, the CAN-FD clock is obtained
>>>    inside the IP itself by dividing the peripheral clock
>>> - the assigned-clocks and assigned-clock-rates properties are specific to
>>>    the CAN-FD clock
>>> the assigned-clocks and assigned-clock-rates properties were dropped
>>> from the required properties list of the Renesas RZ/G3S SoC.
>>>
>>> Add documentation for the Renesas RZ/G3S SoC.
>>>
>>> Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
>>> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>
>> the netdev review bot has found a nitpick, it's about the comment in "rcar_canfd.c". Can you fix it, if
>> you re-spin the series.
>>
>> regards,
>> Marc
>>
>> pw-bot: cr
>>
>> --- Patch [11]: [PATCH net-next 11/37] dt-bindings: can: renesas,rcar-canfd: Document RZ/G3S SoC ---
>> commit 69b4e37d18e5229e1c800b45a5df061af8a98eb9
>> Author: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>
>> dt-bindings: can: renesas,rcar-canfd: Document RZ/G3S SoC
>>
>> This adds the renesas,r9a08g045-canfd compatible for the RZ/G3S CAN FD controller. It adds the compatible
>> to the existing conditional blocks. It also forbids renesas,no-can-fd and renesas,fd-only on RZ/G3S, and
>> makes assigned-clocks and assigned-clock-rates required only for the other SoCs.
>>
>> Link: https://patch.msgid.link/20260902141544.565763-2-claudiu.beznea+renesas@tuxon.dev
>>
>>> diff --git
>>> a/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
>>> b/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
>>> index b9d9dd7a7967..bbaaef8f4282 100644
>>> ---
>>> a/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yaml
>>> +++ b/Documentation/devicetree/bindings/net/can/renesas,rcar-canfd.yam
>>> +++ l
>>
>> [ ... ]
>>
>>> @@ -350,6 +352,20 @@ allOf:
>>>         properties:
>>>           reset-names: false
>>>
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            const: renesas,r9a08g045-canfd
>>> +    then:
>>> +      properties:
>>> +        renesas,no-can-fd: false
>>
>> Discovered by: opus-5-5 · Missed by: fable-5-1, gpt-6-astra, sashiko-gemini · Confirmed by: fable-5-1
>> This isn't a bug, but should the renesas,no-can-fd description be updated to match this new constraint?
>>
>> The property description in the same binding still says that every controller can run in Classical CAN
>> mode:
>>
>>    renesas,no-can-fd:
>>      $ref: /schemas/types.yaml#/definitions/flag
>>      description:
>>        The controller can operate in either CAN-FD mode (default) or FD-Only
>>        mode (RZ/{G2L,G3E} and R-Car Gen4) or Classical CAN mode. Specify this
>>        property to put the controller in Classical CAN mode.
>>
>> With this patch the property is forbidden for renesas,r9a08g045-canfd, because RZ/G3S does not have the
>> mode select bits.
>>
>> The header comment in drivers/net/can/rcar/rcar_canfd.c says the same
>> thing:
>>
>>   * To switch the controller to Classical CAN (CAN 2.0) only mode, add
>>   * "renesas,no-can-fd" optional property to the device tree node. A h/w reset is
>>   * also required to switch modes.
>>
>> Neither text is changed later in the series. Both now contradict the schema for RZ/G3S, and for RZ/G3L
>> once it is added the same way.
>>
>> Could the description exclude the SoCs that only support CAN FD mode?
> 
> 
> Do you plan to update description of renesas,no-canfd in bindings/driver exempting Classical CAN mode
> for RZ/G3S? Or do you want me to update?

I intend to send follow up patches today. If you already have something prepared 
for this, please send it.

Thank you,
Claudiu