Hi Claudiu,

On Fri, 8 Aug 2025 at 13:44, Claudiu Beznea [off-list ref] wrote:

On 09.07.2025 16:43, Krzysztof Kozlowski wrote:

quoted

On 09/07/2025 15:24, Bjorn Helgaas wrote:

quoted

On Wed, Jul 09, 2025 at 08:47:05AM +0200, Krzysztof Kozlowski wrote:

quoted

On 08/07/2025 18:34, Bjorn Helgaas wrote:

quoted

On Fri, Jul 04, 2025 at 07:14:04PM +0300, Claudiu wrote:

quoted

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.

quoted

+++ 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).

Both would be too generic for the myriad of RZ devices.

AFAIU, the R9A08G045Sxx variants are really the same SoC, with some
hardware modules disabled/nonfunctional.  This is typically handled by:
  1. Using the base part number (r9a08g045) in the compatible value,
  2. Having the device node in the base .dtsi,
  3. Deleting nodes in the variant-specific .dtsi file when needed
     (see e.g. arch/arm64/boot/dts/renesas/r9a09g047{,e[35]7}.dtsi)

Hence as R9A08G045S13, R9A08G045S17, R9A08G045S33, and
R9A08G045S37 all have PCIe, I think it is more appropriate
to use "renesas,r9a08g045-pcie" as the compatible value than
"renesas,r9a08g045s33-pcie".

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.

RZ/V2H and RZ/G3E can use "renesas,r9a09g057-pcie" resp.
"renesas,r9a09g047-pcie", with "renesas,r9a08g045-pcie" as a fallback.

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