Re: [PATCH 0/7] iommu: Permit modular builds of ARM SMMU[v3] drivers

[John Garry]

On 31/10/2019 23:34, Saravana Kannan via iommu wrote:
> I looked into the iommu-map property and it shouldn't be too hard to
> add support for it. Looks like we can simply hold off on probing the
> root bridge device till all the iommus in its iommu-map are probed and
> we should be fine.
>
> > I'm also unsure about distro vendors agreeing to a mandatory kernel
> > parameter (of_devlink). Do you plan to eventually enable it by default?
> >
> > > static const struct supplier_bindings of_supplier_bindings[] = {
> > >          { .parse_prop = parse_clocks, },
> > >          { .parse_prop = parse_interconnects, },
> > >          { .parse_prop = parse_regulators, },
> > > +        { .parse_prop = parse_iommus, },
> > >          {},
> > > };
> > >
> > > I plan to upstream this pretty soon, but I have other patches in
> > > flight that touch the same file and I'm waiting for those to get
> > > accepted. I also want to clean up the code a bit to reduce some
> > > repetition before I add support for more bindings.
> > I'm also wondering about ACPI support.
> I'd love to add ACPI support too, but I have zero knowledge of ACPI.
> I'd be happy to help anyone who wants to add ACPI support that allows
> ACPI to add device links.

If possible to add, that may be useful for remedying this:

https://lore.kernel.org/linux-iommu/9625faf4-48ef-2dd3-d82f-931d9cf26976@xxxxxxxxxx/

Thanks,
John

> > IOMMU already has a sort of
> > canonical code path that links endpoints to their IOMMU
> > (iommu_probe_device()), after the firmware descriptions have been parsed.
> > So if we created the device links in the iommu core, for example
> > iommu_bus_notifier(), we would support all firmware interface fl