> -----Original Message----- > From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu- > bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Thierry Reding > Sent: Friday, June 27, 2014 2:20 AM > To: Rob Herring; Pawel Moll; Mark Rutland; Ian Campbell; Kumar Gala; > Stephen Warren; Arnd Bergmann; Will Deacon; Joerg Roedel > Cc: Olav Haugan; devicetree@xxxxxxxxxxxxxxx; Grant Grundler; Rhyland > Klein; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > Marc Zyngier; Allen Martin; Paul Walmsley; linux-tegra@xxxxxxxxxxxxxxx; > Cho KyongHo; Dave Martin; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: [PATCH v3 02/10] devicetree: Add generic IOMMU device tree > bindings > > 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> > --- > Changes in v3: > - use #iommu-cells instead of #address-cells/#size-cells > - drop optional iommu-names property > > Changes in v2: > - add notes about "dma-ranges" property (drop note from commit message) > - document priorities of "iommus" property vs. "dma-ranges" property > - drop #iommu-cells in favour of #address-cells and #size-cells > - remove multiple-master device example > > Documentation/devicetree/bindings/iommu/iommu.txt | 156 > ++++++++++++++++++++++ > 1 file changed, 156 insertions(+) > create mode 100644 Documentation/devicetree/bindings/iommu/iommu.txt > > diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt > b/Documentation/devicetree/bindings/iommu/iommu.txt > new file mode 100644 > index 000000000000..f8f03f057156 > --- /dev/null > +++ b/Documentation/devicetree/bindings/iommu/iommu.txt > @@ -0,0 +1,156 @@ > +This document describes the generic device tree binding for IOMMUs and > +their master(s). > + > + > +IOMMU device node: > +================== > + > +An IOMMU can provide the following services: > + > +* Remap address space to allow devices to access physical memory ranges > +that > + they otherwise wouldn't be capable of accessing. > + > + Example: 32-bit DMA to 64-bit physical addresses > + > +* Implement scatter-gather at page level granularity so that the device > +does > + not have to. > + > +* Provide system protection against "rogue" DMA by forcing all accesses > +to go > + through the IOMMU and faulting when encountering accesses to unmapped > + address regions. > + > +* Provide address space isolation between multiple contexts. > + > + Example: Virtualization > + > +Device nodes compatible with this binding represent hardware with some > +of the above capabilities. > + > +IOMMUs can be single-master or multiple-master. Single-master IOMMU > +devices typically have a fixed association to the master device, > +whereas multiple- master IOMMU devices can translate accesses from more > than one master. > + > +The device tree node of the IOMMU device's parent bus must contain a > +valid "dma-ranges" property that describes how the physical address > +space of the IOMMU maps to memory. An empty "dma-ranges" property means > +that there is a > +1:1 mapping from IOMMU to memory. > + > +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. > +- #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. > +- #iommu-cells = <4>: Some IOMMU devices allow the DMA window for > +masters to > + be configured. The first cell of the address in this may contain the > +master > + device's ID for example, while the second cell could contain the > +start of > + the DMA window for the given device. The length of the DMA window is > +given > + by the third and fourth cells. > + > + > +IOMMU master node: > +================== > + > +Devices that access memory through an IOMMU are called masters. A > +device can have multiple master interfaces (to one or more IOMMU > devices). > + > +Required properties: > +-------------------- > +- iommus: A list of phandle and IOMMU specifier pairs that describe the > +IOMMU > + master interfaces of the device. One entry in the list describes one > +master > + interface of the device. > + > +When an "iommus" property is specified in a device tree node, the IOMMU > +will be used for address translation. If a "dma-ranges" property exists > +in the device's parent node it will be ignored. An exception to this > +rule is if the referenced IOMMU is disabled, in which case the > +"dma-ranges" property of the parent shall take effect. > + > + > +Notes: > +====== > + > +One possible extension to the above is to use an "iommus" property > +along with a "dma-ranges" property in a bus device node (such as PCI > +host bridges). This can be useful to describe how children on the bus > +relate to the IOMMU if they are not explicitly listed in the device > +tree (e.g. PCI devices). However, the requirements of that use-case > +haven't been fully determined yet. Implementing this is therefore not > +recommended without further discussion and extension of this binding. > + > + > +Examples: > +========= > + > +Single-master IOMMU: > +-------------------- > + > + iommu { > + #iommu-cells = <0>; > + }; > + > + master { > + iommus = <&/iommu>; > + }; > + > +Multiple-master IOMMU with fixed associations: > +---------------------------------------------- > + > + /* multiple-master IOMMU */ > + iommu { > + /* > + * Masters are statically associated with this IOMMU and > + * address translation is always enabled. > + */ > + #iommu-cells = <0>; > + }; > + > + /* static association with IOMMU */ > + master@1 { > + reg = <1>; > + iommus = <&/iommu>; > + }; > + > + /* static association with IOMMU */ > + master@2 { > + reg = <2>; > + iommus = <&/iommu>; > + }; > + > +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>; > + }; > + Master node corresponds to the device node, right? Master ID would correspond to Stream ID? We are already using "iommu-parent" property to link a device to its corresponding IOMMU. We can use the same property instead of using "iommus". -Varun -- 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
