On 28.02.2014 10:54, Marek Szyprowski wrote:

Hello,

On 2014-02-26 12:51, Grant Likely wrote:

quoted

On Fri, 21 Feb 2014 13:25:17 +0100, Marek Szyprowski
[off-list ref] wrote:

quoted

From: Grant Likely <redacted>

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 <redacted>
[joshc: Based on binding document proposed (in non-patch form) here:

http://lkml.kernel.org/g/20131030134702.19B57C402A0@trevor.secretlab.ca

quoted

 adapted to support #memory-region-cells]
Signed-off-by: Josh Cartwright <redacted>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 .../bindings/reserved-memory/reserved-memory.txt   |  138

++++++++++++++++++++

quoted

 1 file changed, 138 insertions(+)
 create mode 100644

Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

quoted

diff --git

a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

quoted

new file mode 100644
index 000000000000..a606ce90c9c4

--- /dev/null
+++

b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

quoted

@@ -0,0 +1,138 @@
+*** Reserved memory regions ***
+
+Reserved memory is specified as a node under the /reserved-memory

node.

quoted

+The operating system shall exclude reserved memory from normal usage
+one can create child nodes describing particular reserved (excluded

from

quoted

+normal use) memory regions. Such memory regions are usually

designed for

quoted

+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

quoted

+                                  nodes memory-region specifier

I still don't like this portion of the binding. I'm not convinced that
it is necessary in the majority of cases and it is going to be very
driver specific. I would rather drop it entirely from the common
binding. If a specific driver needs to do something like the above then
it can have a driver specific binding. Otherwise I think the default
should be a simple phandle with no arguments to a single reserved memory
node.

Ben, can you weigh in on the current state of this document. I'm mostly
happy with it aside from my comment above. Do you think this is ready to
be merged?

quoted

+ranges (required) - standard definition
+    - Should be empty
+
+/reserved-memory/ child nodes
+-----------------------------
+Each child of the reserved-memory node specifies one or more

regions of

quoted

+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.

quoted

+
+Following the generic-names recommended practice, node names should
+reflect the purpose of the node (ie. "framebuffer" or "dma-pool").

Unit

quoted

+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.

quoted

+   alloc-ranges (optional) - prop-encoded-array (address, length

pairs).

quoted

+                           - Specifies regions of memory that are
+                             acceptable to allocate from.
+
+If both reg and size are present, then the reg property takes

precedence

quoted

+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

quoted

+          used as a shared pool of DMA buffers for a set of

devices. It can

quoted

+          be used by an operating system to instanciate the

necessary pool

quoted

+          management subsystem if necessary.
+        - vendor specific string in the form

<vendor>,[<device>-]<usage>

Add "Use vendor strings to identify regions dedicates for a specific
vendor device. For example: 'acme,framebuffer'. Platform code can use
vendor
strings to identify device specific regions"

So do you want to completely drop phandle based links between device
nodes and
memory regions?

Huh? How this would work with regions that have to be used for multiple 
(but not all - not a default region) devices?

Best regards,
Tomasz