Re: [PATCH 02/16] dt-bindings: soc: renesas: renesas,rzg2l-sysc: Add #reset-cells for RZ/G3S

[Conor Dooley <conor@kernel.org>]

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On Fri, Aug 23, 2024 at 07:26:42PM +0300, claudiu beznea wrote:
> On 23.08.2024 19:18, Conor Dooley wrote:
> > On Fri, Aug 23, 2024 at 10:54:06AM +0300, claudiu beznea wrote:
> >> Hi, Conor,
> >>
> >> On 22.08.2024 19:42, Conor Dooley wrote:
> >>> On Thu, Aug 22, 2024 at 06:27:47PM +0300, Claudiu wrote:
> >>>> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> >>>>
> >>>> The RZ/G3S System controller has registers to control signals that need
> >>>> to be de-asserted/asserted before/after different SoC areas are power
> >>>> on/off. This signals are implemented as reset signals. For this document
> >>>> the #reset-cells property.
> >>>>
> >>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> >>>> ---
> >>>>  .../bindings/soc/renesas/renesas,rzg2l-sysc.yaml | 16 ++++++++++++++++
> >>>>  1 file changed, 16 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml b/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml
> >>>> index 4386b2c3fa4d..6b0bb34485d9 100644
> >>>> --- a/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml
> >>>> +++ b/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml
> >>>> @@ -42,12 +42,28 @@ properties:
> >>>>        - const: cm33stbyr_int
> >>>>        - const: ca55_deny
> >>>>  
> >>>> +  "#reset-cells":
> >>>> +    const: 1
> >>>> +
> >>>>  required:
> >>>>    - compatible
> >>>>    - reg
> >>>>  
> >>>>  additionalProperties: false
> >>>>  
> >>>> +allOf:
> >>>> +  - if:
> >>>> +      properties:
> >>>> +        compatible:
> >>>> +          contains:
> >>>> +            const: renesas,r9a08g045-sysc
> >>>> +    then:
> >>>> +      required:
> >>>> +        - "#reset-cells"
> >>>
> >>> Given this is new required property on an existing platform, I'd expect
> >>> some mention of why it used to be okay to not have this but is now
> >>> required. Did firmware or a bootloader stage take things out of reset?
> >>
> >> On previous SoCs the SYS controller has no support for controlling the
> >> signals going to different peripherals (USB, PCIE in case of RZ/G3S).
> >> I'll add a note about this on next version.
> > 
> > My initial thought here wasn't about previous SoCs though, it was
> > because you didn't add the compatible in this series for /this/ SoC.
> 
> RZ/G3S compatible is already present in this file:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml#n26

I know, first thing I did when I read the original patch was open the
file ;)
I don't care about the old SoCs, cos you're not applying the property to
them, so what's changed between SoCs isn't really relevant. It's a mention
of why, on this SoC, it is safe to add new required properties that I want.

AFAIU the answer is that no consumer of the resets existed before, so
there's not some special state there, and I am guessing that the new
sysc driver you're adding isn't going to fail to probe if there are no
resets, it just won't register a reset controller? Which is fine, cos all
devicetrees that have the new peripherals will have #reset-cells etc.

> > What's worth noting isn't about the prior SoCs, it is about what makes
> > it okay for this one.

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