cma: Add support for memory limits

Currently, when dynamically placing regions CMA will allow the memory
to be placed anywhere, including highmem. Due to system restrictions,
regions may need to be placed in a smaller range. Add support to
devicetree to allow these regions to have an upper bound on where they
will be placed.

Change-Id: Ib4ae194cbb6389e1091e7e04cfd331e9ab67ad05
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

Documentation/devicetree/bindings/memory.txt

@@ -37,6 +37,7 @@ wit the following convention:
 	(linux,contiguous-region);
 	(linux,default-contiguous-region);
 	(linux,reserve-region);
+	(linux,memory-limit);
         label = (unique_name);
 };
 
@@ -52,6 +53,11 @@ linux,default-contiguous-region: property indicating that the region
 linux,reserve-region: property indicating that the contiguous memory will
 		not be given back to the system allocator. The memory be
 		always be available for contiguous use.
+linux,memory-limit: property specifying an upper bound on the physical address
+		of the region if the region is placed dynamically. If no limit
+		is specificed, the region may be placed anywhere in the physical
+		address space. 0 may be used to specify lowmem (i.e. the region
+		will be placed in the direct mapped lowmem region)
 label:		an internal name used for automatically associating the
 		cma region with a given device. The label is optional;
 		if the label is not given the client is responsible for

drivers/base/dma-contiguous.c

@@ -222,6 +222,7 @@ int __init cma_fdt_scan(unsigned long node, const char *uname,
 	bool in_system;
 	unsigned long size_cells = dt_root_size_cells;
 	unsigned long addr_cells = dt_root_addr_cells;
+	phys_addr_t limit = MEMBLOCK_ALLOC_ANYWHERE;
 
 	if (!of_get_flat_dt_prop(node, "linux,contiguous-region", NULL))
 		return 0;
@@ -245,9 +246,13 @@ int __init cma_fdt_scan(unsigned long node, const char *uname,
 	in_system =
 		of_get_flat_dt_prop(node, "linux,reserve-region", NULL) ? 0 : 1;
 
-	pr_info("Found %s, memory base %lx, size %ld MiB\n", uname,
-		(unsigned long)base, (unsigned long)size / SZ_1M);
-	dma_contiguous_reserve_area(size, &base, MEMBLOCK_ALLOC_ANYWHERE, name,
+	prop = of_get_flat_dt_prop(node, "linux,memory-limit", NULL);
+	if (prop)
+		limit = be32_to_cpu(prop[0]);
+
+	pr_info("Found %s, memory base %lx, size %ld MiB, limit %pa\n", uname,
+		(unsigned long)base, (unsigned long)size / SZ_1M, &limit);
+	dma_contiguous_reserve_area(size, &base, limit, name,
 					in_system);
 
 	return 0;