linux-kernel - Re: [PATCH v5 2/7] dt-bindings: PCI: qcom,pcie-sc7280: Make elbi register as an optional

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Message-ID: <20250310-rainbow-ebony-panda-cd0ad3@krzk-bin>
Date: Mon, 10 Mar 2025 10:31:49 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: cros-qcom-dts-watchers@...omium.org, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kw@...ux.com>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	quic_vbadigan@...cinc.com, quic_mrana@...cinc.com, quic_vpernami@...cinc.com, 
	mmareddy@...cinc.com
Subject: Re: [PATCH v5 2/7] dt-bindings: PCI: qcom,pcie-sc7280: Make elbi
 register as an optional

On Sun, Mar 09, 2025 at 11:15:24AM +0530, Krishna Chaitanya Chundru wrote:
> ELBI regitsers are optional registers and not been using in this

What does it mean "optional"? Hardware can miss them or they can be
restricted by firmware? Which board has such issue?

Your commit must explain this.

> platform. Having this register as required is not allowing to enable
> ECAM feature of the PCIe cleanly. ECAM feature needs to do single
> remap of entire 256MB which includes DBI and ELBI. Having optional
> ELBI registers in the devicetree and binding is causing resorce
> conflicts when enabling ECAM feature.

I don't think it is possible that register in binding causes anything.
Linux does not parse the binding doc. You are changing bindings based on
some issues in your drivers.

Fix your drivers.


> 
> So, make ELBI registers as optional one.
> 
> Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>  Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml b/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> index 76cb9fbfd476..326059a59b61 100644
> --- a/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> +++ b/Documentation/devicetree/bindings/pci/qcom,pcie-sc7280.yaml
> @@ -19,17 +19,17 @@ properties:
>      const: qcom,pcie-sc7280
>  
>    reg:
> -    minItems: 5
> +    minItems: 4
>      maxItems: 6
>  
>    reg-names:
> -    minItems: 5
> +    minItems: 4
>      items:
>        - const: parf # Qualcomm specific registers
>        - const: dbi # DesignWare PCIe registers
> -      - const: elbi # External local bus interface registers
>        - const: atu # ATU address space
>        - const: config # PCIe configuration space
> +      - const: elbi # External local bus interface registers

NAK, ABI break based on issues on drivers. Fix your drivers.

Best regards,
Krzysztof