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# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/reserved-memory/reserved-memory.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: /reserved-memory Child Node Common
maintainers:
- devicetree-spec@vger.kernel.org
description: >
Reserved memory is specified as a node under the /reserved-memory node. The
operating system shall exclude reserved memory from normal usage one can
create child nodes describing particular reserved (excluded from normal use)
memory regions. Such memory regions are usually designed for the special
usage by various device drivers.
Each child of the reserved-memory node specifies one or more regions
of reserved memory. Each child node may either use a 'reg' property to
specify a specific range of reserved memory, or a 'size' property with
optional constraints to request a dynamically allocated block of
memory.
Following the generic-names recommended practice, node names should
reflect the purpose of the node (ie. "framebuffer" or "dma-pool").
Unit address (@<address>) should be appended to the name if the node
is a static allocation.
properties:
reg: true
size:
$ref: /schemas/types.yaml#/definitions/uint32-array
minItems: 1
maxItems: 2
description: >
Length based on parent's \#size-cells. Size in bytes of memory to
reserve.
alignment:
$ref: /schemas/types.yaml#/definitions/uint32-array
minItems: 1
maxItems: 2
description: >
Length based on parent's \#size-cells. Address boundary for
alignment of allocation.
alloc-ranges:
$ref: /schemas/types.yaml#/definitions/uint32-array
description: >
Address and Length pairs. Specifies regions of memory that are
acceptable to allocate from.
iommu-addresses:
$ref: /schemas/types.yaml#/definitions/phandle-array
description: >
A list of phandle and specifier pairs that describe static IO virtual
address space mappings and carveouts associated with a given reserved
memory region. The phandle in the first cell refers to the device for
which the mapping or carveout is to be created.
The specifier consists of an address/size pair and denotes the IO
virtual address range of the region for the given device. The exact
format depends on the values of the "#address-cells" and "#size-cells"
properties of the device referenced via the phandle.
When used in combination with a "reg" property, an IOVA mapping is to
be established for this memory region. One example where this can be
useful is to create an identity mapping for physical memory that the
firmware has configured some hardware to access (such as a bootsplash
framebuffer).
If no "reg" property is specified, the "iommu-addresses" property
defines carveout regions in the IOVA space for the given device. This
can be useful if a certain memory region should not be mapped through
the IOMMU.
no-map:
type: boolean
description: >
Indicates the operating system must not create a virtual mapping
of the region as part of its standard mapping of system memory,
nor permit speculative access to it under any circumstances other
than under the control of the device driver using the region.
reusable:
type: boolean
description: >
The operating system can use the memory in this region with the
limitation that the device driver(s) owning the region need to be
able to reclaim it back. Typically that means that the operating
system can use that region to store volatile or cached data that
can be otherwise regenerated or migrated elsewhere.
allOf:
- if:
required:
- no-map
then:
not:
required:
- reusable
- if:
required:
- reusable
then:
not:
required:
- no-map
oneOf:
- oneOf:
- required:
- reg
- required:
- size
- oneOf:
# IOMMU reservations
- required:
- iommu-addresses
# IOMMU mappings
- required:
- reg
- iommu-addresses
additionalProperties: true
examples:
- |
/ {
compatible = "foo";
model = "foo";
#address-cells = <2>;
#size-cells = <2>;
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
adsp_resv: reservation-adsp {
/*
* Restrict IOVA mappings for ADSP buffers to the 512 MiB region
* from 0x40000000 - 0x5fffffff. Anything outside is reserved by
* the ADSP for I/O memory and private memory allocations.
*/
iommu-addresses = <&adsp 0x0 0x00000000 0x00 0x40000000>,
<&adsp 0x0 0x60000000 0xff 0xa0000000>;
};
fb: framebuffer@90000000 {
reg = <0x0 0x90000000 0x0 0x00800000>;
iommu-addresses = <&dc0 0x0 0x90000000 0x0 0x00800000>;
};
};
bus@0 {
#address-cells = <1>;
#size-cells = <1>;
ranges = <0x0 0x0 0x0 0x40000000>;
adsp: adsp@2990000 {
reg = <0x2990000 0x2000>;
memory-region = <&adsp_resv>;
};
dc0: display@15200000 {
reg = <0x15200000 0x10000>;
memory-region = <&fb>;
};
};
};
...
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