Hi,
On Fri, Aug 09, 2013 at 01:51:58PM +0200, Marek Szyprowski wrote:
Add device tree support for contiguous and reserved memory regions defined in device tree. Initialization is done in 2 steps. First, the memory is reserved, what happens very early when only flattened device tree is available. Then on device initialization the corresponding cma and reserved regions are assigned to each device structure.
Bikeshedding on some wording, mostly in case you have to respin for other reasons.
diff --git a/Documentation/devicetree/bindings/memory.txt b/Documentation/devicetree/bindings/memory.txt new file mode 100644 index 0000000..167d013 --- /dev/null +++ b/Documentation/devicetree/bindings/memory.txt @@ -0,0 +1,152 @@ +*** Memory binding ***
+The /memory node provides basic information about the address and size +of the physical memory. This node is usually filled or updated by the +bootloader, depending on the actual memory configuration of the given +hardware.
+The memory layout is described by the folllowing node:
+memory {
- device_type = "memory";
- reg = <(baseaddr1) (size1)
(baseaddr2) (size2)...(baseaddrN) (sizeN)>;+};
+baseaddrX: the base address of the defined memory bank +sizeX: the size of the defined memory bank
+More than one memory bank can be defined.
+*** Reserved memory regions ***
+In /memory/reserved-memory node one can create additional nodes
There's really no requirement on naming here. We should instead search all of /memory for the compatible properties.
+describing particular reserved (excluded from normal use) memory +regions. Such memory regions are usually designed for the special usage +by various device drivers. A good example are contiguous memory +allocations or memory sharing with other operating system on the same +hardware board. Those special memory regions might depend on the board +configuration and devices used on the target system.
+Parameters for each memory region can be encoded into the device tree +wit the following convention:
+[(label):] (name)@(address) {
@(unit-address)
- compatible = "contiguous-memory-region", "reserved-memory-region";
- reg = <(address) (size)>;
- (linux,default-contiguous-region);
+};
+label: label given to the defined region (optional) +name: an name given to the defined region +address: the base address of the defined region
unit-address. It's optional unless there are conflicting node names.
+size: the size of the memory region
+compatible: "contiguous-memory-region" - enables binding of this
region to Contiguous Memory Allocator (special region forcontiguous memory allocations, shared with movable systemmemory, Linux kernel-specific), alternatively if"reserved-memory-region" - compatibility is defined, givenregion is assigned for exclusive usage for DMA transfers
"reserved-memory-region" isn't necessarily just for DMA transfers, it can be used pretty much for anything. pstore comes to mind.
+linux,default-contiguous-region: property indicating that the region
is the default region for all contiguous memoryallocations, Linux specific (optional)
Hmm. We handle some of these defaults such as device naming (i2c busses, etc) through /alias nodes. Maybe it would be more consistent to do that here too, by providing a phandle there instead.
+Each defined region must use unique name.
Hmm, this is quite different from how memory nodes work, and it'd be nice to keep similar semantics. A "name" property would make more sense for areas that need to be named, but even then, why do names here matter? References should be by phandle, not by name. So I think it should likely just be scrapped.
It is optional to specify the +base address, so if one wants to use autoconfiguration of the base +address, he must specify the '0' as base address in the 'reg' property +and assign ann unique name to such regions.
"an unique"
But I don't think this is a good idea, since it violates basic use of the reg properties, where you usually don't have overlaps, and no real requirements on names (as mentioned above).
-Olof