Re: [PATCH v6 01/11] of: document bindings for reserved-memory nodes

[Grant Likely]

On Fri, 28 Feb 2014 14:42:46 +0100, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote:
> From: Grant Likely <grant.likely@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> [joshc: Based on binding document proposed (in non-patch form) here:
>  http://lkml.kernel.org/g/20131030134702.19B57C402A0@xxxxxxxxxxxxxxxxxxx
>  adapted to support #memory-region-cells]
> Signed-off-by: Josh Cartwright <joshc@xxxxxxxxxxxxxx>
> [mszyprow: removed #memory-region-cells property]
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

Merged, thanks.

g.

> ---
>  .../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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