Re: [PATCH v2 1/5] dt-bindings: PCI: Add STM32MP25 PCIe root complex bindings

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Dec 03, 2024 at 04:25:15PM -0600, Bjorn Helgaas wrote:
> On Tue, Nov 26, 2024 at 04:51:15PM +0100, Christian Bruel wrote:
> > Document the bindings for STM32MP25 PCIe Controller configured in
> > root complex mode.
> > 
> > Supports 4 legacy interrupts and MSI interrupts from the ARM
> > GICv2m controller.
> 
> s/legacy/INTx/
> 
> > STM32 PCIe may be in a power domain which is the case for the STM32MP25
> > based boards.
> > 
> > Supports wake# from wake-gpios
> 
> s/wake#/WAKE#/
> 
> > +  wake-gpios:
> > +    description: GPIO controlled connection to WAKE# input signal
> 
> I'm not a hardware guy, but this sounds like a GPIO that *reads*
> WAKE#, not controls it.
> 
> > +    pcie@48400000 {
> > +        compatible = "st,stm32mp25-pcie-rc";
> > +        device_type = "pci";
> > +        num-lanes = <1>;
> 
> num-lanes applies to a Root Port, not to a Root Complex.  I know most
> bindings conflate Root Ports with the Root Complex, maybe because many
> of these controllers only support a single Root Port?
> 
> But are we ever going to separate these out?  I assume someday
> controllers will support multiple Root Ports and/or additional devices
> on the root bus, like RCiEPs, RCECs, etc., and we'll need per-RP phys,
> max-link-speed, num-lanes, reset-gpios, etc.
> 
> Seems like it would be to our benefit to split out the Root Ports when
> we can, even if the current hardware only supports one, so we can
> start untangling the code and data structures.
> 

+1 for moving the properties to RP node where they should belong to. The
controller driver might have to do some extra work to parse the RP node and get
these properties, but it is worth the effort.

- Mani

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