linux-kernel - Re: [PATCH v3 1/6] dt-bindings: PCI: Add binding for qps615

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Message-ID: <20250210075813.c2wvr3bozndi2ice@thinkpad>
Date: Mon, 10 Feb 2025 13:28:13 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
Cc: Rob Herring <robh@...nel.org>, andersson@...nel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	cros-qcom-dts-watchers@...omium.org,
	Jingoo Han <jingoohan1@...il.com>,
	Bartosz Golaszewski <brgl@...ev.pl>, quic_vbadigan@...cinc.com,
	linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/6] dt-bindings: PCI: Add binding for qps615

On Tue, Jan 07, 2025 at 07:58:17PM +0530, Krishna Chaitanya Chundru wrote:
> 
> 
> On 12/30/2024 11:52 PM, Manivannan Sadhasivam wrote:
> > On Mon, Dec 23, 2024 at 08:57:37PM +0200, Dmitry Baryshkov wrote:
> > 
> > [...]
> > 
> > > > This switch allows us to configure both upstream, downstream ports and
> > > > also embedded Ethernet port which is internal to the switch. These
> > > > properties are applicable for all of those.
> > > > > > +
> > > > > > +    allOf:
> > > > > > +      - $ref: /schemas/pci/pci-bus.yaml#
> > > > > 
> > > > > pci-pci-bridge.yaml is more specific and closer to what this device is.
> > > > > 
> > > > I tried this now, I was getting warning saying the compatible
> > > > /local/mnt/workspace/skales/kobj/Documentation/devicetree/bindings/pci/qcom,qps615.example.dtb:
> > > > pcie@0,0: compatible: ['pci1179,0623'] does not contain items matching the
> > > > given schema
> > > >          from schema $id: http://devicetree.org/schemas/pci/qcom,qps615.yaml#
> > > > /local/mnt/workspace/skales/kobj/Documentation/devicetree/bindings/pci/qcom,qps615.example.dtb:
> > > > pcie@0,0: Unevaluated properties are not allowed ('#address-cells',
> > > > '#size-cells', 'bus-range', 'device_type', 'ranges' were unexpected)
> > > > 
> > > > I think pci-pci-bridge is expecting the compatible string in this format
> > > > only "pciclass,0604".
> > > 
> > > I think the pci-pci-bridge schema requires to have "pciclass,0604" among
> > > other compatibles. So you should be able to do something like:
> > > 
> > > compatible = "pci1179,0623", "pciclass,0604";
> > > 
> > 
> > Even though a PCIe switch is supposed to be a network of PCI bridges, using
> > PCI bridge fallback for this switch is not technically correct IMO. Mostly
> > because, this switch requires other configurations which are not applicable to
> > PCI bridges. So the drivers matching against the bridge compatible won't be able
> > to use this switch.
> > 
> > - Mani
> Rob,
> 
> Using pci-pci-bridge expects to use compatible as pciclass,0604, we
> can't  use as this switch is doing other configurations which are
> applicable to PCI bridges. can we continue to use pci-bus.yaml.
> 

Let's put it the other way. What are the blockers in using the
pci-pci-bridge.yaml other than the fallback compatible? If the compatible is the
only blocker, you can add it even though the drivers cannot make use of it
(that's one of the reason why I was against adding it).

- Mani

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