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Message-Id: <1390417133-6650-5-git-send-email-joshc@codeaurora.org>
Date: Wed, 22 Jan 2014 12:58:52 -0600
From: Josh Cartwright <joshc@...eaurora.org>
To: Grant Likely <grant.likely@...aro.org>,
Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org,
Marek Szyprowski <m.szyprowski@...sung.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Laura Abbott <lauraa@...eaurora.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Rob Landley <rob@...dley.net>, devicetree@...r.kernel.org,
linux-doc@...r.kernel.org
Subject: [PATCH RFC 4/4] of: document bindings for reserved-memory nodes
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.
[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]
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Laura Abbott <lauraa@...eaurora.org>
Signed-off-by: Josh Cartwright <joshc@...eaurora.org>
---
Hey Grant-
Seeing as you are the primary author of this binding, with only a few minor
changes on my part, I've marked you as the commit author. Let me know if
that's a problem.
Josh
.../bindings/reserved-memory/reserved-memory.txt | 137 +++++++++++++++++++++
1 file changed, 137 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 0000000..7cd7829
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
@@ -0,0 +1,137 @@
+*** 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
+#memory-region-cells (required) - dictates number of cells used in the child
+ nodes memory-region specifier
+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";
+ #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>;
+ /* ... */
+ };
+};
--
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