Re: [PATCH v3 4/9] dt-bindings: PCI: renesas,r9a08g045s33-pcie: Add documentation for the PCIe IP on Renesas RZ/G3S

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

Hi, all,

Apologies for the late reply.


On 09.07.2025 16:43, Krzysztof Kozlowski wrote:
> On 09/07/2025 15:24, Bjorn Helgaas wrote:
>> On Wed, Jul 09, 2025 at 08:47:05AM +0200, Krzysztof Kozlowski wrote:
>>> On 08/07/2025 18:34, Bjorn Helgaas wrote:
>>>> On Fri, Jul 04, 2025 at 07:14:04PM +0300, Claudiu wrote:
>>>>> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>>>>
>>>>> The PCIe IP available on the Renesas RZ/G3S complies with the PCI Express
>>>>> Base Specification 4.0. It is designed for root complex applications and
>>>>> features a single-lane (x1) implementation. Add documentation for it.
>>>>
>>>>> +++ b/Documentation/devicetree/bindings/pci/renesas,r9a08g045s33-pcie.yaml
>>>>
>>>> The "r9a08g045s33" in the filename seems oddly specific.  Does it
>>>> leave room for descendants of the current chip that will inevitably be
>>>> added in the future?  Most bindings are named with a fairly generic
>>>> family name, e.g., "fsl,layerscape", "hisilicon,kirin", "intel,
>>>> keembay", "samsung,exynos", etc.
>>>>
>>>
>>> Bindings should be named by compatible, not in a generic way, so name is
>>> correct. It can always grow with new compatibles even if name matches
>>> old one, it's not a problem.
>>
>> Ok, thanks!
>>
>> I guess that means I'm casting shade on the "r9a08g045s33" compatible.
>> I suppose it means something to somebody.
> 
> Well, I hope it matches the name of the SoC, from which the compatible
> should come :)

The r9a08g45s33 is the part number of a device from the RZ/G3S group. This
particular device from RZ/G3S group supports PCIe.

In the RZ/G3S group there are more SoC variants (each with its own part
number). Not all support PCIe. To differentiate b/w PCIe and non-PCIe
variants it has been chosen to use the full part number here.

The available RZ/G3S part numbers are listed in Table 1.1 Product Lineup at [1]

(The following steps should be followed to access the manual:
1/ Click the "User Manual" button
2/ Click "Confirm"; this will start downloading an archive
3/ Open the downloaded archive
4/ Navigate to r01uh1014ej*-rzg3s-users-manual-hardware -> Deliverables
5/ Open the file r01uh1014ej*-rzg3s.pdf)

We use a similar compatible scheme in other drivers.

Geert, I may be wrong. Please correct me otherwise, as I don't have the
full picture of this.

Maybe, the other variant would be to use "renesas,rzg3s-pcie", or maybe a
more generic one "renesas,rz-pcie" (though I think this last one is too
generic).

Geert, please let us know if you have some suggestions here with regards to
the compatible. The IP on RZ/G3S is compatible also with the one in RZ/V2H,
RZ/G3E.

Thank you,
Claudiu

[1]
https://www.renesas.com/en/products/rz-g3s?queryID=695cc067c2d89e3f271d43656ede4d12

> 
> Best regards,
> Krzysztof