linux-kernel - Re: [PATCH v3 1/5] dt-bindings: pci: Add Sophgo SG2042 PCIe host

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Message-ID: <20250219182247.GA225989@bhelgaas>
Date: Wed, 19 Feb 2025 12:22:47 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Chen Wang <unicorn_wang@...look.com>
Cc: Chen Wang <unicornxw@...il.com>, kw@...ux.com,
	u.kleine-koenig@...libre.com, aou@...s.berkeley.edu, arnd@...db.de,
	bhelgaas@...gle.com, conor+dt@...nel.org, guoren@...nel.org,
	inochiama@...look.com, krzk+dt@...nel.org, lee@...nel.org,
	lpieralisi@...nel.org, manivannan.sadhasivam@...aro.org,
	palmer@...belt.com, paul.walmsley@...ive.com, pbrobinson@...il.com,
	robh@...nel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-riscv@...ts.infradead.org, chao.wei@...hgo.com,
	xiaoguang.xing@...hgo.com, fengchun.li@...hgo.com
Subject: Re: [PATCH v3 1/5] dt-bindings: pci: Add Sophgo SG2042 PCIe host

On Wed, Feb 12, 2025 at 01:54:11PM +0800, Chen Wang wrote:
> On 2025/2/12 12:25, Bjorn Helgaas wrote:
> [......]
> > > pcie_rc1 and pcie_rc2 share registers in cdns_pcie1_ctrl. By using
> > > different "sophgo,core-id" values, they can distinguish and access
> > > the registers they need in cdns_pcie1_ctrl.
> > Where does cdns_pcie1_ctrl fit in this example?  Does that enclose
> > both pcie_rc1 and pcie_rc2?
> 
> cdns_pcie1_ctrl is defined as a syscon node,  which contains registers
> shared by pcie_rc1 and pcie_rc2. In the binding yaml file, I drew a diagram
> to describe the relationship between them, copy here for your quick
> reference:
> 
> +                     +-- Core (Link0) <---> pcie_rc1  +-----------------+
> +                     |                                |                 |
> +      Cadence IP 2 --+                                | cdns_pcie1_ctrl |
> +                     |                                |                 |
> +                     +-- Core (Link1) <---> pcie_rc2  +-----------------+
> 
> The following is an example with cdns_pcie1_ctrl added. For simplicity, I
> deleted pcie_rc0.

Looks good.  It would be nice if there were some naming similarity or
comment or other hint to connect sophgo,core-id with the syscon node.

> pcie_rc1: pcie@...2000000 {
>     compatible = "sophgo,sg2042-pcie-host";
>     ...... // host bride level properties
>     linux,pci-domain = <1>;
>     sophgo,core-id = <0>;
>     sophgo,syscon-pcie-ctrl = <&cdns_pcie1_ctrl>;
>     port {
>         // port level properties
>         vendor-id = <0x1f1c>;
>         device-id = <0x2042>;
>         num-lanes = <2>;
>     };
> };
> 
> pcie_rc2: pcie@...2800000 {
>     compatible = "sophgo,sg2042-pcie-host";
>     ...... // host bride level properties
>     linux,pci-domain = <2>;
>     sophgo,core-id = <1>;
>     sophgo,syscon-pcie-ctrl = <&cdns_pcie1_ctrl>;
>     port {
>         // port level properties
>         vendor-id = <0x1f1c>;
>         device-id = <0x2042>;
>         num-lanes = <2>;
>     }
> 
> };
> 
> cdns_pcie1_ctrl: syscon@...3800000 {
>     compatible = "sophgo,sg2042-pcie-ctrl", "syscon";
>     reg = <0x70 0x63800000 0x0 0x800000>;
> };
>