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

Christian Bruel
2024-12-05T13:46:12Z

On 12/3/24 23:25, 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.

Rephrasing as
"GPIO used as WAKE# input signal" (output for the endpoint bindings)

>
>> + 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.

OK. and we support only 1 lane anyway, so drop it.

thanks,

>
> Bjorn