From 44680eedf9409daf0fed618ae101f35d1f83d1a4 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Wed, 25 Jun 2014 11:29:12 +0100 Subject: iommu/arm-smmu: remove support for chained SMMUs The ARM SMMU driver has supported chained SMMUs (i.e. SMMUs connected back-to-back in series) via the smmu-parent property in device tree. This was in anticipation of somebody building such a configuration, however that seems not to be the case. This patch removes the unused chained SMMU hack from the driver. We can consider adding it back later if somebody decided they need it, but for the time being it's just pointless mess that we're carrying in mainline. Removal of the feature also makes migration to the generic IOMMU bindings easier. Signed-off-by: Will Deacon --- Documentation/devicetree/bindings/iommu/arm,smmu.txt | 6 ------ 1 file changed, 6 deletions(-) (limited to 'Documentation/devicetree/bindings/iommu') diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt index f284b99402bc..2d0f7cd867ea 100644 --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt @@ -42,12 +42,6 @@ conditions. ** System MMU optional properties: -- smmu-parent : When multiple SMMUs are chained together, this - property can be used to provide a phandle to the - parent SMMU (that is the next SMMU on the path going - from the mmu-masters towards memory) node for this - SMMU. - - calxeda,smmu-secure-config-access : Enable proper handling of buggy implementations that always use secure access to SMMU configuration registers. In this case non-secure -- cgit v1.2.3 From 1a5b5376442bd6c23b5722ecdc7242fcc61ce338 Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Thu, 31 Jul 2014 12:43:03 +0200 Subject: devicetree: Add generic IOMMU device tree bindings 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 Acked-by: Will Deacon Reviewed-by: Arnd Bergmann Acked-by: Rob Herring Signed-off-by: Thierry Reding Reviewed-by: Mark Rutland Reviewed-by: Olof Johansson Acked-by: Laurent Pinchart Signed-off-by: Joerg Roedel --- Documentation/devicetree/bindings/iommu/iommu.txt | 182 ++++++++++++++++++++++ 1 file changed, 182 insertions(+) create mode 100644 Documentation/devicetree/bindings/iommu/iommu.txt (limited to 'Documentation/devicetree/bindings/iommu') diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt b/Documentation/devicetree/bindings/iommu/iommu.txt new file mode 100644 index 000000000000..5a8b4624defc --- /dev/null +++ b/Documentation/devicetree/bindings/iommu/iommu.txt @@ -0,0 +1,182 @@ +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. + +The meaning of the IOMMU specifier is defined by the device tree binding of +the specific IOMMU. Below are a few examples of typical use-cases: + +- #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. Note that an IOMMU can by design + be multi-master yet only expose a single master in a given configuration. + In such cases the number of cells will usually be 1 as in the next case. +- #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. In some cases more than + one cell can be required to represent a single master 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. + +Note that these are merely examples and real-world use-cases may use different +definitions to represent their individual needs. Always refer to the specific +IOMMU binding for the exact meaning of the cells that make up the specifier. + + +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. Note that merely disabling a device tree node does +not guarantee that the IOMMU is really disabled since the hardware may not +have a means to turn off translation. But it is invalid in such cases to +disable the IOMMU's device tree node in the first place because it would +prevent any driver from properly setting up the translations. + + +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 share + * the same address translations because the IOMMU does not + * have sufficient information to distinguish between masters. + * + * Consequently address translation is always on or off for + * all masters at any given point in time. + */ + #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@1 { + /* device has master ID 42 in the IOMMU */ + iommus = <&{/iommu} 42>; + }; + + master@2 { + /* device has master IDs 23 and 24 in the IOMMU */ + iommus = <&{/iommu} 23>, <&{/iommu} 24>; + }; + +Multiple-master IOMMU with configurable DMA window: +--------------------------------------------------- + + / { + iommu { + /* + * One cell for the master ID and one cell for the + * address of the DMA window. The length of the DMA + * window is encoded in two cells. + * + * The DMA window is the range addressable by the + * master (i.e. the I/O virtual address space). + */ + #iommu-cells = <4>; + }; + + master { + /* master ID 42, 4 GiB DMA window starting at 0 */ + iommus = <&{/iommu} 42 0 0x1 0x0>; + }; + }; -- cgit v1.2.3