Re: [PATCH 9/9] ARM: dts: uniphier: Remove compatible "snps,dw-pcie-ep" from Pro5 pcie-ep node

[Kunihiko Hayashi]

On 2022/08/03 15:11, Krzysztof Kozlowski wrote:
> On 02/08/2022 15:10, Kunihiko Hayashi wrote:
> > On 2022/08/02 17:33, Krzysztof Kozlowski wrote:
> > > On 30/07/2022 13:58, Arnd Bergmann wrote:
> > > > On Mon, Jul 4, 2022 at 2:20 AM Kunihiko Hayashi
> > > > <hayashi.kunihiko@xxxxxxxxxxxxx> wrote:
> > > > > UniPhier PCIe endpoint controller doesn't use "snps,dw-pcie-ep"
> > > > > compatible,
> > > > > so this is no longer needed. Remove the compatible string from the
> > > > > pcie-ep
> > > > > node to fix the following warning.
> > > > >
> > > > >     uniphier-pro5-epcore.dtb: pcie@66000000: compatible:
> > > > > ['socionext,uniphier-pro5-pcie-ep', 'snps,dw-pcie-ep'] is too long
> > > > >         From schema:
> > > > > Documentation/devicetree/bindings/pci/socionext,uniphier-pcie-ep.yaml
> > > >
> > > > This sounds like a problem with the binding rather than the dt file. Is
> > > > this not
> > > > a designware pci endpoint? Should it be documented in that binding
> > > > instead?
> >
> > In term of the binding, it seems that the current binding doesn't allow
> > descriptions
> > that list two compatibles. There is something wrong with the binding.
> >
> > > Depends. We had one or two similar cases, where we dropped the snps/dw
> > > generic compatible, because device was actually quite different and
> > > could not match against snps/dw compatible. IOW, if device bound/matched
> > > via generic compatible it would be entirely non-operational. Logically I
> > > think it is okay to drop the generic compatible. Different question is
> > > any ABI break.
> >
> > In term of the controller, we can add dw general compatible if the more
> > generic
> > driver (pcie-designware-plat) works on the controller.
> >
> > However, the generic driver can't do the initialization what the
> > controller
> > needs, so we can add controller-specific compatible only.
> > The commit bf2942a8b7c3 ("arm64: tegra: Fix Tegra194 PCIe EP compatible
> > string")
> > removes the generic compatible for the same reason.
> >
> > This patch suggests removing the generic compatible for the former reason,
> > though, I might suggest it for the controller reason.
>
> The patch does not explain this, though.

Yes, I'll resend the patch with an explanation of the reason for the controller
like Tegra194.

Thank you,

---
Best Regards
Kunihiko Hayashi