1 files changed, 51 insertions, 11 deletions

diff --git a/mm/cma.c b/mm/cma.c
index a951a3b..963bc4a 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -143,6 +143,54 @@ static int __init cma_init_reserved_areas(void)
 core_initcall(cma_init_reserved_areas);
 
 /**
+ * cma_init_reserved_mem() - create custom contiguous area from reserved memory
+ * @base: Base address of the reserved area
+ * @size: Size of the reserved area (in bytes),
+ * @order_per_bit: Order of pages represented by one bit on bitmap.
+ * @res_cma: Pointer to store the created cma region.
+ *
+ * This function creates custom contiguous area from already reserved memory.
+ */
+int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
+				 int order_per_bit, struct cma **res_cma)
+{
+	struct cma *cma;
+	phys_addr_t alignment;
+
+	/* Sanity checks */
+	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
+		pr_err("Not enough slots for CMA reserved regions!\n");
+		return -ENOSPC;
+	}
+
+	if (!size || !memblock_is_region_reserved(base, size))
+		return -EINVAL;
+
+	/* ensure minimal alignment requied by mm core */
+	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
+
+	/* alignment should be aligned with order_per_bit */
+	if (!IS_ALIGNED(alignment >> PAGE_SHIFT, 1 << order_per_bit))
+		return -EINVAL;
+
+	if (ALIGN(base, alignment) != base || ALIGN(size, alignment) != size)
+		return -EINVAL;
+
+	/*
+	 * Each reserved area must be initialised later, when more kernel
+	 * subsystems (like slab allocator) are available.
+	 */
+	cma = &cma_areas[cma_area_count];
+	cma->base_pfn = PFN_DOWN(base);
+	cma->count = size >> PAGE_SHIFT;
+	cma->order_per_bit = order_per_bit;
+	*res_cma = cma;
+	cma_area_count++;
+
+	return 0;
+}
+
+/**
  * cma_declare_contiguous() - reserve custom contiguous area
  * @base: Base address of the reserved area optional, use 0 for any
  * @size: Size of the reserved area (in bytes),
@@ -165,7 +213,6 @@ int __init cma_declare_contiguous(phys_addr_t base,
 			phys_addr_t alignment, unsigned int order_per_bit,
 			bool fixed, struct cma **res_cma)
 {
-	struct cma *cma;
 	phys_addr_t memblock_end = memblock_end_of_DRAM();
 	phys_addr_t highmem_start = __pa(high_memory);
 	int ret = 0;
@@ -237,16 +284,9 @@ int __init cma_declare_contiguous(phys_addr_t base,
 		}
 	}
 
-	/*
-	 * Each reserved area must be initialised later, when more kernel
-	 * subsystems (like slab allocator) are available.
-	 */
-	cma = &cma_areas[cma_area_count];
-	cma->base_pfn = PFN_DOWN(base);
-	cma->count = size >> PAGE_SHIFT;
-	cma->order_per_bit = order_per_bit;
-	*res_cma = cma;
-	cma_area_count++;
+	ret = cma_init_reserved_mem(base, size, order_per_bit, res_cma);
+	if (ret)
+		goto err;
 
 	pr_info("Reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
 		(unsigned long)base);