linux-kernel - Re: [PATCH] dt-bindings: PCI: snps,dw-pcie: Drop "#interrupt-cells" from example

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Message-ID: <CAL_JsqJY43z5exVft4vYvbrMSoVFFD4E7KVJ+isC1mdQ5H3=CA@mail.gmail.com>
Date: Tue, 19 Nov 2024 11:26:57 -0600
From: Rob Herring <robh@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Jingoo Han <jingoohan1@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>, linux-pci@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: PCI: snps,dw-pcie: Drop "#interrupt-cells"
 from example

On Tue, Nov 19, 2024 at 11:04 AM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
>
> On Fri, Nov 15, 2024 at 08:07:07AM -0600, Rob Herring wrote:
> > On Fri, Nov 15, 2024 at 1:26 AM Manivannan Sadhasivam
> > <manivannan.sadhasivam@...aro.org> wrote:
> > >
> > > On Tue, Nov 05, 2024 at 03:32:16PM -0600, Rob Herring (Arm) wrote:
> > > > "#interrupt-cells" is not valid without a corresponding "interrupt-map"
> > > > or "interrupt-controller" property. As the example has neither, drop
> > > > "#interrupt-cells". This fixes a dtc interrupt_provider warning.
> > > >
> > >
> > > But the DWC controllers have an in-built MSI controller. Shouldn't we add
> > > 'interrrupt-controller' property then?
> >
> > Why? Is that needed for the MSI controller to function? I don't think so.
> >
>
> No. I was asking from bindings perspective.
>
> > Now we do have "interrupt-controller" present for a number of MSI
> > providers. I suspect that's there to get OF_DECLARE to work, but I
> > doubt we really need MSI controllers initialized early.
> >
>
> Again no, for this case. I was under the assumption that all interrupt
> providers should have the 'interrupt-controller' property in their nodes.

Yes. What interrupts is the DW controller providing? Only the PCI
legacy interrupts which are optional. An msi-controller and an
interrupt-controller are 2 distinct providers. An MSI provider is not
an interrupt provider, but an interrupt consumer. Some bindings define
both, but I think many of those cases are probably wrong.

Rob