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

[Manivannan Sadhasivam]

On Fri, Feb 21, 2025 at 04:13:30PM -0600, Bjorn Helgaas wrote:
> [cc->to: Rob]
> 
> On Fri, Feb 21, 2025 at 11:29:20AM +0800, Chen Wang wrote:
> > On 2025/2/20 2:22, Bjorn Helgaas wrote:
> > > 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@7062000000 {
> > > >      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@7062800000 {
> > > >      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@7063800000 {
> > > >      compatible = "sophgo,sg2042-pcie-ctrl", "syscon";
> > > >      reg = <0x70 0x63800000 0x0 0x800000>;
> > > > };
> > 
> > I find dtb check will report error due to "port" is not a evaulated property
> > for pcie host. Should we add a vendror specific property for this?
> > 
> > Or do you have any example for reference?
> 

'port' is not a valid node name. It should be 'pcie' and should have the unit
address corresponding to the bridge BDF. Please refer DT nodes of other
platforms:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/sm8450.dtsi#n2071

- Mani

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