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Message-Id: <20140302050012.8F71DC40372@trevor.secretlab.ca>
Date: Sun, 02 Mar 2014 13:00:12 +0800
From: Grant Likely <grant.likely@...aro.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linaro-mm-sig@...ts.linaro.org, devicetree@...r.kernel.org,
linux-doc@...r.kernel.org
Cc: Marek Szyprowski <m.szyprowski@...sung.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Arnd Bergmann <arnd@...db.de>,
Michal Nazarewicz <mina86@...a86.com>,
Tomasz Figa <t.figa@...sung.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Laura Abbott <lauraa@...eaurora.org>,
Rob Herring <robh+dt@...nel.org>,
Olof Johansson <olof@...om.net>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Stephen Warren <swarren@...dotorg.org>,
Ian Campbell <ian.campbell@...rix.com>,
Tomasz Figa <tomasz.figa@...il.com>,
Kumar Gala <galak@...eaurora.org>,
Nishanth Peethambaran <nishanth.p@...il.com>,
Marc <marc.ceeeee@...il.com>,
Josh Cartwright <joshc@...eaurora.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH v6 01/11] of: document bindings for reserved-memory nodes
On Fri, 28 Feb 2014 14:42:46 +0100, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
> From: Grant Likely <grant.likely@...aro.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@...aro.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@...eaurora.org>
> [mszyprow: removed #memory-region-cells property]
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
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@...00000 and 64MiB in size),
> +one dedicated to the framebuffer device (named framebuffer@...00000, 8MiB), and
> +one for multimedia processing (named multimedia-memory@...00000, 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@...00000 {
> + #memory-region-cells = <0>;
> + reg = <0x78000000 0x800000>;
> + };
> +
> + multimedia_reserved: multimedia@...00000 {
> + compatible = "acme,multimedia-memory";
> + #memory-region-cells = <1>;
> + reg = <0x77000000 0x4000000>;
> + };
> + };
> +
> + /* ... */
> +
> + fb0: video@...00000 {
> + memory-region = <&display_reserved>;
> + /* ... */
> + };
> +
> + scaler: scaler@...00000 {
> + memory-region = <&multimedia_reserved 0xdeadbeef>;
> + /* ... */
> + };
> +
> + codec: codec@...00000 {
> + memory-region = <&multimedia_reserved 0xfeebdaed>;
> + /* ... */
> + };
> +};
> --
> 1.7.9.5
>
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