Hi Thierry, On Thu, Jun 26, 2014 at 09:49:42PM +0100, Thierry Reding wrote: > From: Thierry Reding <treding@xxxxxxxxxx> > > This commit introduces a generic device tree binding for IOMMU devices. > Only a very minimal subset is described here, but it is enough to cover > the requirements of both the Exynos System MMU and Tegra SMMU as > discussed here: > > https://lkml.org/lkml/2014/4/27/346 > > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> [...] > +Required properties: > +-------------------- > +- #iommu-cells: The number of cells in an IOMMU specifier needed to encode an > + address. > + > +Typical values for the above include: > +- #iommu-cells = <0>: Single master IOMMU devices are not configurable and > + therefore no additional information needs to be encoded in the specifier. > + This may also apply to multiple master IOMMU devices that do not allow the > + association of masters to be configured. A multiple-master capable IOMMU could be built with a single master, but we'd still need #iommu-cells > 0 here. I appreciate this is just an example, but the wording sounds like it's enforced. > +- #iommu-cells = <1>: Multiple master IOMMU devices may need to be configured > + in order to enable translation for a given master. In such cases the single > + address cell corresponds to the master device's ID. Again, we will definitely need more than one cell in this case, as I fully expect multiple StreamIDs for each master (e.g. Qualcomm mentioned on the list the other day that they have a master emitting 43 unique IDs). Anyway, the actual binding looks great, I just don't want people to think they need to do something different because they don't fit your example use-cases. > +Multiple-master IOMMU: > +---------------------- > + > + iommu { > + /* the specifier represents the ID of the master */ > + #iommu-cells = <1>; > + }; > + > + master { > + /* device has master ID 42 in the IOMMU */ > + iommus = <&/iommu 42>; > + }; > + > +Multiple-master IOMMU with configurable DMA window: > +--------------------------------------------------- > + > + / { > + #address-cells = <1>; > + #size-cells = <1>; > + > + iommu { > + /* master ID, address and length of DMA window */ > + #iommu-cells = <4>; > + }; > + > + master { > + /* master ID 42, 4 GiB DMA window starting at 0 */ > + iommus = <&/iommu 42 0 0x1 0x0>; > + }; > + }; Could you also please include an example of a master with multiple IDs? Will -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
