> -----Original Message----- > From: Stuart Yoder > Sent: Friday, December 16, 2016 8:07 AM > To: Mark Rutland <mark.rutland@xxxxxxx>; robin.murphy@xxxxxxx; > will.deacon@xxxxxxx > Cc: robh+dt@xxxxxxxxxx; Bharat Bhushan <bharat.bhushan@xxxxxxx>; > Nipun Gupta <nipun.gupta@xxxxxxx>; Diana Madalina Craciun > <diana.craciun@xxxxxxx>; devicetree@xxxxxxxxxxxxxxx; iommu@lists.linux- > foundation.org > Subject: RFC: extend iommu-map binding to support #iommu-cells > 1 > > For context, please see the thread: > https://www.spinics.net/lists/arm-kernel/msg539066.html > > The existing iommu-map binding did not account for the situation where > #iommu-cells == 2, as permitted in the ARM SMMU binding. The 2nd cell of > the IOMMU specifier being the SMR mask. The existing binding defines the > mapping as: > Any RID r in the interval [rid-base, rid-base + length) is associated with > the listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base). > > ...and that does not work if iommu-base is 2 cells, the second being the SMR > mask. > > While this can be worked around by always having length=1, it seems we can > get this cleaned up by updating the binding definition for iommu-map. > > See patch below. Thoughts? > > Thanks, > Stuart > > ------------------------------------------------------------------------- > > diff --git a/Documentation/devicetree/bindings/pci/pci-iommu.txt > b/Documentation/devicetree/bindings/pci/pci-iommu.txt > index 56c8296..e81b461 100644 > --- a/Documentation/devicetree/bindings/pci/pci-iommu.txt > +++ b/Documentation/devicetree/bindings/pci/pci-iommu.txt > @@ -38,8 +38,20 @@ Optional properties > The property is an arbitrary number of tuples of > (rid-base,iommu,iommu-base,length). > > - Any RID r in the interval [rid-base, rid-base + length) is associated with > - the listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base). > + If the associated IOMMU has an #iommu-cells value of 1, any RID r in > + the interval [rid-base, rid-base + length) is associated with the > + listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base). > + > + ARM SMMU Note: > + The ARM SMMU binding permits an #iommu-cells value of 2 and in this > + case defines an IOMMU specifier to be: (stream-id,smr-mask) > + > + In an iommu-map this means the iommu-base consists of 2 cells: > + (rid-base,iommu,[stream-id,smr-mask],length). > + > + In this case the RID to IOMMU specifier mapping is defined to be: > + any RID r in the interval [rid-base, rid-base + length) is associated > + with the listed IOMMU, with the iommu-specifier (r - rid-base + stream- > id). Should not this be (r - rid-base + (stream-id & smr-mask)) ? So basically stream-id ranges from (stream-id & smr-mask) - (stream-id & smr-mask + (length - 1) ) Thanks -Bharat > > - iommu-map-mask: A mask to be applied to each Requester ID prior to > being > mapped to an iommu-specifier per the iommu-map property. > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
