On 08/23/2013 02:39 AM, wrote:
From: Marek Szyprowski m.szyprowski@samsung.com
This patch adds device tree support for contiguous and reserved memory regions defined in device tree.
Large memory blocks can be reliably reserved only during early boot. This must happen before the whole memory management subsystem is initialized, because we need to ensure that the given contiguous blocks are not yet allocated by kernel. Also it must happen before kernel mappings for the whole low memory are created, to ensure that there will be no mappings (for reserved blocks) or mapping with special properties can be created (for CMA blocks). This all happens before device tree structures are unflattened, so we need to get reserved memory layout directly from fdt.
Later, those reserved memory regions are assigned to devices on each device structure initialization.
I think the binding looks OK now; just a couple minor comments below.
diff --git a/Documentation/devicetree/bindings/memory.txt b/Documentation/devicetree/bindings/memory.txt
+*** Reserved memory regions ***
+compatible: one or more of:
- "linux,contiguous-memory-region" - enables binding of this
region to Contiguous Memory Allocator (special region forcontiguous memory allocations, shared with movable systemmemory, Linux kernel-specific).
- "reserved-memory-region" - compatibility is defined, given
region is assigned for exclusive usage for by the respectivedevices.
I'm slightly hesitant to agree with "linux" in the name here, since it seems like the concept of a memory region where DMA buffers/... should be allocated is pretty OS-independant. Similar for:
+linux,default-contiguous-region: property indicating that the region
- is the default region for all contiguous memory
- allocations, Linux specific (optional)
But, I guess there's nothing stopping any other OS from parsing this same property, so I suppose it's OK. What do other DT maintainers think?
+*** Example ***
reserved-memory {
...
contig_region@0 {
...
display_mem: region@78000000 {
...
multimedia_mem: region@77000000 {
Nit: I think all 3 of those nodes should be called region, but it's probably fine as-is.
So, the binding, Acked-by: Stephen Warren swarren@nvidia.com