RE: [PATCH v7 1/2] dt-bindings: PCI: amd-mdb: Add CPM6 support

[Musham, Sai Krishna]

AMD General

Hi Rob,

> -----Original Message-----
> From: Rob Herring <robh@xxxxxxxxxx>
> Sent: Friday, September 18, 2026 12:55 AM
> To: Musham, Sai Krishna <sai.krishna.musham@xxxxxxx>
> Cc: bhelgaas@xxxxxxxxxx; lpieralisi@xxxxxxxxxx; kw@xxxxxxxxx;
> mani@xxxxxxxxxx; krzk+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx;
> cassel@xxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Simek, Michal <michal.simek@xxxxxxx>;
> Gogada, Bharat Kumar <bharat.kumar.gogada@xxxxxxx>; Havalige,
> Thippeswamy <thippeswamy.havalige@xxxxxxx>; Sanwal, Pranav
> <Pranav.sanwal@xxxxxxx>
> Subject: Re: [PATCH v7 1/2] dt-bindings: PCI: amd-mdb: Add CPM6 support
>
> On Sun, Aug 23, 2026 at 09:37:14AM +0530, Sai Krishna Musham wrote:
> > The AMD CPM6 PCIe controller is based on the Synopsys DesignWare PCIe
> > IP and integrates two PCIe host controller instances. Add the
> > "amd,versal2-cpm6-host" and "amd,versal2-cpm6-host1" compatible strings
> > to describe the HOST0 and HOST1 controller instances.
>
> That is clear from the diff. What's not clear in this patch, and I
> probably already asked, what is the difference between host0 and host1?
> Usually instances are not different compatibles...
>

Thanks for reviewing, there is no functional difference between HOST0 and
HOST1. They are two instances of the same CPM6 PCIe controller and support
the same feature set.

The underlying hardware and driver behavior are identical between the
two instances. The only differences are instance-specific resources,
such as register regions and controller-specific interrupt status bits.

I understand your point that instances are typically not represented by
different compatible strings. Given that the driver needs to distinguish
between the two controller instances for these instance-specific
resources, could you please suggest the preferred DT representation for
this case?

Thanks,
Sai Krishna

> Rob