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    Subject[PATCH v6 01/11] of: document bindings for reserved-memory nodes
    Date
    From: Grant Likely <grant.likely@linaro.org>

    Reserved memory nodes allow for the reservation of static (fixed
    address) regions, or dynamically allocated regions for a specific
    purpose.

    Signed-off-by: Grant Likely <grant.likely@linaro.org>
    [joshc: Based on binding document proposed (in non-patch form) here:
    http://lkml.kernel.org/g/20131030134702.19B57C402A0@trevor.secretlab.ca
    adapted to support #memory-region-cells]
    Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
    [mszyprow: removed #memory-region-cells property]
    Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
    ---
    .../bindings/reserved-memory/reserved-memory.txt | 136 ++++++++++++++++++++
    1 file changed, 136 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

    diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
    new file mode 100644
    index 000000000000..8b0d747a38e7
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
    @@ -0,0 +1,136 @@
    +*** Reserved memory regions ***
    +
    +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.
    +
    +Parameters for each memory region can be encoded into the device tree
    +with the following nodes:
    +
    +/reserved-memory node
    +---------------------
    +#address-cells, #size-cells (required) - standard definition
    + - Should use the same values as the root node
    +ranges (required) - standard definition
    + - Should be empty
    +
    +/reserved-memory/ child nodes
    +-----------------------------
    +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:
    +Requires either a) or b) below.
    +a) static allocation
    + reg (required) - standard definition
    +b) dynamic allocation
    + size (required) - length based on parent's #size-cells
    + - Size in bytes of memory to reserve.
    + alignment (optional) - length based on parent's #size-cells
    + - Address boundary for alignment of allocation.
    + alloc-ranges (optional) - prop-encoded-array (address, length pairs).
    + - Specifies regions of memory that are
    + acceptable to allocate from.
    +
    +If both reg and size are present, then the reg property takes precedence
    +and size is ignored.
    +
    +Additional properties:
    +compatible (optional) - standard definition
    + - may contain the following strings:
    + - shared-dma-pool: This indicates a region of memory meant to be
    + used as a shared pool of DMA buffers for a set of devices. It can
    + be used by an operating system to instanciate the necessary pool
    + management subsystem if necessary.
    + - vendor specific string in the form <vendor>,[<device>-]<usage>
    +no-map (optional) - empty property
    + - 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 (optional) - empty property
    + - 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.
    +
    +Linux implementation note:
    +- If a "linux,cma-default" property is present, then Linux will use the
    + region for the default pool of the contiguous memory allocator.
    +
    +Device node references to reserved memory
    +-----------------------------------------
    +Regions in the /reserved-memory node may be referenced by other device
    +nodes by adding a memory-region property to the device node.
    +
    +memory-region (optional) - phandle, specifier pairs to children of /reserved-memory
    +
    +Example
    +-------
    +This example defines 3 contiguous regions are defined for Linux kernel:
    +one default of all device drivers (named linux,cma@72000000 and 64MiB in size),
    +one dedicated to the framebuffer device (named framebuffer@78000000, 8MiB), and
    +one for multimedia processing (named multimedia-memory@77000000, 64MiB).
    +
    +/ {
    + #address-cells = <1>;
    + #size-cells = <1>;
    +
    + memory {
    + reg = <0x40000000 0x40000000>;
    + };
    +
    + reserved-memory {
    + #address-cells = <1>;
    + #size-cells = <1>;
    + ranges;
    +
    + /* global autoconfigured region for contiguous allocations */
    + linux,cma {
    + compatible = "shared-dma-pool";
    + reusable;
    + #memory-region-cells = <0>;
    + size = <0x4000000>;
    + alignment = <0x2000>;
    + linux,cma-default;
    + };
    +
    + display_reserved: framebuffer@78000000 {
    + #memory-region-cells = <0>;
    + reg = <0x78000000 0x800000>;
    + };
    +
    + multimedia_reserved: multimedia@77000000 {
    + compatible = "acme,multimedia-memory";
    + #memory-region-cells = <1>;
    + reg = <0x77000000 0x4000000>;
    + };
    + };
    +
    + /* ... */
    +
    + fb0: video@12300000 {
    + memory-region = <&display_reserved>;
    + /* ... */
    + };
    +
    + scaler: scaler@12500000 {
    + memory-region = <&multimedia_reserved 0xdeadbeef>;
    + /* ... */
    + };
    +
    + codec: codec@12600000 {
    + memory-region = <&multimedia_reserved 0xfeebdaed>;
    + /* ... */
    + };
    +};
    --
    1.7.9.5


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