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dt-bindings: iommu: dart: Support specifying the DMA aperture

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Apple DARTs are often connected directly to devices that expect only a
portion of their address space to be used for DMA (for example, because
other ranges are mapped directly to something else).

Follow the "#iommu-cells = <4>" example from iommu.txt and allow
specifying the DMA aperture via additional cells. Since DART is used on
64-bit Apple silicon systems use two cells to specify the start and
length of the aperture. A common aperture starts at 0x100_0000_0000
and spans a 36-bit address space.

This corresponds to the vm-base and vm-size properties on the Apple
device tree side of things.

As not all devices require this and to keep compatibility with existing
device trees allow 1 and 5 as values for #iommu-cells.

Signed-off-by: Janne Grunau <j@jannau.net>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Janne Grunau 2026-09-02 21:18:54 +02:00 committed by Joerg Roedel
parent 93f51579e7
commit 4d520541fe
1 changed files with 7 additions and 5 deletions
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12
Documentation/devicetree/bindings/iommu/apple,dart.yaml
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@ -44,10 +44,12 @@ properties:
Optional since not all IOMMUs are attached to a clock gate.
'#iommu-cells':
const: 1
enum: [ 1, 5 ]
description:
Has to be one. The single cell describes the stream id emitted by
a master to the IOMMU.
Has to be one or five. The first cell describes the stream id emitted by
a master to the IOMMU. The optional second and third cell describe the
aperture start of a master's DMA window and fourth and fifth cell describe
the size of DMA window.
power-domains:
maxItems: 1
@ -66,11 +68,11 @@ examples:
compatible = "apple,t8103-dart";
reg = <0x82f80000 0x4000>;
interrupts = <1 781 4>;
#iommu-cells = <1>;
#iommu-cells = <5>;
};
master1 {
iommus = <&dart1 0>;
iommus = <&dart1 0 0x100 0x0 0x10 0x0>;
};
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