Re: [PATCH 02/10] dt-bindings: PCI: qcom: Do not require 'msi-map-mask'

Johan Hovold
2024-02-20T08:42:19Z

On Tue, Feb 20, 2024 at 08:41:25AM +0100, Johan Hovold wrote:
> On Fri, Feb 16, 2024 at 10:24:06PM +0530, Manivannan Sadhasivam wrote:

> > msi-map-mask is definitely needed as it would allow all the devices under the
> > same bus to reuse the MSI identifier. Currently, excluding this property will
> > not cause any issue since there is a single device under each bus. But we cannot
> > assume that is going to be the case on all boards.
>
> Are you saying that there is never a use case for an identity mapping?
> Just on Qualcomm hardware or in general?
>
> It looks like we have a fairly large number of mainline devicetrees that
> do use an identity mapping here (i.e. do not specify 'msi-map-mask') and
> the binding document also has an explicit example of this.
>
> Documentation/devicetree/bindings/pci/pci-msi.txt

The above should have said "linear mapping" as the msi-base is not
always identical to the rid-base, but you get the point.

Johan