On Fri, May 22, 2020 at 3:57 AM Diana Craciun OSS
<diana.craciun@xxxxxxxxxxx> wrote:
>
> On 5/22/2020 12:42 PM, Robin Murphy 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.
>
> Right, will change it.
>
> >
> >>> +
> >>> + 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.
>
> Before adding msi-map, the fsl-mc code assumed that ICID and streamID
> are equal and used msi-parent just to get the reference to the ITS node.
> Removing msi-parent will break the backward compatibility of the already
> existing systems. Maybe we should mention that this is legacy and not to
> be used for newer device trees.
If ids are 1:1, then the DT should use msi-parent. If there is
remapping, then use msi-map. A given system should use one or the
other. I suppose if some ids are 1:1 and the msi-map was added to add
additional support for ids not 1:1, then you could end up with both.
That's fine in dts files, but examples should reflect the 'right' way.
Rob
