On Fri, May 22, 2020 at 3:42 AM Robin Murphy <robin.murphy@xxxxxxx> wrote:
>
> On 2020-05-22 00:10, Rob Herring wrote:
> > On Thu, May 21, 2020 at 7:00 AM Lorenzo Pieralisi
> > <lorenzo.pieralisi@xxxxxxx> wrote:
> >>
> >> From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> >>
> >> The existing bindings cannot be used to specify the relationship
> >> between fsl-mc devices and GIC ITSes.
> >>
> >> Add a generic binding for mapping fsl-mc devices to GIC ITSes, using
> >> msi-map property.
> >>
> >> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> >> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> >> ---
> >> .../devicetree/bindings/misc/fsl,qoriq-mc.txt | 30 +++++++++++++++++--
> >> 1 file changed, 27 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >> index 9134e9bcca56..b0813b2d0493 100644
> >> --- a/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >> +++ b/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
> >> @@ -18,9 +18,9 @@ same hardware "isolation context" and a 10-bit value called an ICID
> >> the requester.
> >>
> >> The generic 'iommus' property is insufficient to describe the relationship
> >> -between ICIDs and IOMMUs, so an iommu-map property is used to define
> >> -the set of possible ICIDs under a root DPRC and how they map to
> >> -an IOMMU.
> >> +between ICIDs and IOMMUs, so the iommu-map and msi-map properties are used
> >> +to define the set of possible ICIDs under a root DPRC and how they map to
> >> +an IOMMU and a GIC ITS respectively.
> >>
> >> For generic IOMMU bindings, see
> >> Documentation/devicetree/bindings/iommu/iommu.txt.
> >> @@ -28,6 +28,9 @@ Documentation/devicetree/bindings/iommu/iommu.txt.
> >> For arm-smmu binding, see:
> >> Documentation/devicetree/bindings/iommu/arm,smmu.yaml.
> >>
> >> +For GICv3 and GIC ITS bindings, see:
> >> +Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml.
> >> +
> >> Required properties:
> >>
> >> - compatible
> >> @@ -119,6 +122,15 @@ Optional properties:
> >> associated with the listed IOMMU, with the iommu-specifier
> >> (i - icid-base + iommu-base).
> >>
> >> +- msi-map: Maps an ICID to a GIC ITS and associated iommu-specifier
> >> + data.
> >> +
> >> + The property is an arbitrary number of tuples of
> >> + (icid-base,iommu,iommu-base,length).
> >
> > I'm confused because the example has GIC ITS phandle, not an IOMMU.
> >
> > What is an iommu-base?
>
> Right, I was already halfway through writing a reply to say that all the
> copy-pasted "iommu" references here should be using the terminology from
> the pci-msi.txt binding instead.
>
> >> +
> >> + Any ICID in the interval [icid-base, icid-base + length) is
> >> + associated with the listed GIC ITS, with the iommu-specifier
> >> + (i - icid-base + iommu-base).
> >> Example:
> >>
> >> smmu: iommu@5000000 {
> >> @@ -128,6 +140,16 @@ Example:
> >> ...
> >> };
> >>
> >> + gic: interrupt-controller@6000000 {
> >> + compatible = "arm,gic-v3";
> >> + ...
> >> + its: gic-its@6020000 {
> >> + compatible = "arm,gic-v3-its";
> >> + msi-controller;
> >> + ...
> >> + };
> >> + };
> >> +
> >> fsl_mc: fsl-mc@80c000000 {
> >> compatible = "fsl,qoriq-mc";
> >> reg = <0x00000008 0x0c000000 0 0x40>, /* MC portal base */
> >> @@ -135,6 +157,8 @@ Example:
> >> msi-parent = <&its>;
>
> Side note: is it right to keep msi-parent here? It rather implies that
> the MC itself has a 'native' Device ID rather than an ICID, which I
> believe is not strictly true. Plus it's extra-confusing that it doesn't
> specify an ID either way, since that makes it look like the legacy PCI
> case that gets treated implicitly as an identity msi-map, which makes no
> sense at all to combine with an actual msi-map.
No, it doesn't make sense from a binding perspective.
>
> >> /* define map for ICIDs 23-64 */
> >> iommu-map = <23 &smmu 23 41>;
> >> + /* define msi map for ICIDs 23-64 */
> >> + msi-map = <23 &its 23 41>;
> >
> > Seeing 23 twice is odd. The numbers to the right of 'its' should be an
> > ITS number space.
>
> On about 99% of systems the values in the SMMU Stream ID and ITS Device
> ID spaces are going to be the same. Nobody's going to bother carrying
> *two* sets of sideband data across the interconnect if they don't have to ;)
I'm referring to the 23 on the left and right, not between the msi and
iommu. If the left and right are the same, then what are we remapping
exactly?
Rob
