linux-kernel - Re: [PATCH v5 4/5] arm64: dts: qcom: ipq5332: Add PCIe related nodes

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Message-ID: <20250108183235.GA220566@bhelgaas>
Date: Wed, 8 Jan 2025 12:32:35 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Varadarajan Narayanan <quic_varada@...cinc.com>
Cc: bhelgaas@...gle.com, lpieralisi@...nel.org, kw@...ux.com,
	manivannan.sadhasivam@...aro.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, vkoul@...nel.org,
	kishon@...nel.org, andersson@...nel.org, konradybcio@...nel.org,
	p.zabel@...gutronix.de, quic_nsekar@...cinc.com,
	dmitry.baryshkov@...aro.org, linux-arm-msm@...r.kernel.org,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
	Praveenkumar I <quic_ipkumar@...cinc.com>,
	Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v5 4/5] arm64: dts: qcom: ipq5332: Add PCIe related nodes

On Thu, Jan 02, 2025 at 05:00:18PM +0530, Varadarajan Narayanan wrote:
> From: Praveenkumar I <quic_ipkumar@...cinc.com>
> 
> Add phy and controller nodes for pcie0_x1 and pcie1_x2.

> +		pcie1: pcie@...00000 {
> +			compatible = "qcom,pcie-ipq5332", "qcom,pcie-ipq9574";
> +			reg = <0x00088000 0x3000>,
> +			      <0x18000000 0xf1d>,
> +			      <0x18000f20 0xa8>,
> +			      <0x18001000 0x1000>,
> +			      <0x18100000 0x1000>,
> +			      <0x0008b000 0x1000>;
> +			reg-names = "parf",
> +				    "dbi",
> +				    "elbi",
> +				    "atu",
> +				    "config",
> +				    "mhi";
> +			device_type = "pci";
> +			linux,pci-domain = <1>;
> +			bus-range = <0x00 0xff>;

This bus-range isn't needed, is it?  pci_parse_request_of_pci_ranges()
should default to 0x00-0xff if no bus-range property is present.

> +			num-lanes = <2>;
> +			phys = <&pcie1_phy>;
> +			phy-names = "pciephy";

I think num-lanes and PHY info are per-Root Port properties, not a
host controller properties, aren't they?  Some of the clock and reset
properties might also be per-Root Port.

Ideally, I think per-Root Port properties should be in a child device
as they are here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pci/mvebu-pci.txt?id=v6.12#n137
but it looks like the num-lanes parsing is done in
dw_pcie_get_resources(), which can only handle a single num-lanes per
DWC controller, so maybe it's impractical to add a child device here.

But I wonder if it would be useful to at least group the per-Root Port
things together in the binding to help us start thinking about the
difference between the controller and the Root Port(s).

Bjorn