On 28.02.2014 10:54, Marek Szyprowski wrote:
Hello,
On 2014-02-26 12:51, Grant Likely wrote:
On Fri, 21 Feb 2014 13:25:17 +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>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
> .../bindings/reserved-memory/reserved-memory.txt | 138
++++++++++++++++++++
> 1 file changed, 138 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..a606ce90c9c4
> --- /dev/null
> +++
b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
> @@ -0,0 +1,138 @@
> +*** 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
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?
> +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>
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
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