genalloc:support allocating specific region

Add new algo for genalloc, it reserve a specific region of
memory
Signed-off-by: NZhao Qiang <qiang.zhao@freescale.com>
Signed-off-by: NScott Wood <scottwood@freescale.com>

include/linux/genalloc.h

@@ -84,6 +84,13 @@ struct genpool_data_align {
 	int align;		/* alignment by bytes for starting address */
 };
 
+/*
+ *  gen_pool data descriptor for gen_pool_fixed_alloc.
+ */
+struct genpool_data_fixed {
+	unsigned long offset;		/* The offset of the specific region */
+};
+
 extern struct gen_pool *gen_pool_create(int, int);
 extern phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long);
 extern int gen_pool_add_virt(struct gen_pool *, unsigned long, phys_addr_t,
@@ -124,6 +131,10 @@ extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
 		unsigned long start, unsigned int nr, void *data,
 		struct gen_pool *pool);
 
+extern unsigned long gen_pool_fixed_alloc(unsigned long *map,
+		unsigned long size, unsigned long start, unsigned int nr,
+		void *data, struct gen_pool *pool);
+
 extern unsigned long gen_pool_first_fit_align(unsigned long *map,
 		unsigned long size, unsigned long start, unsigned int nr,
 		void *data, struct gen_pool *pool);

lib/genalloc.c

@@ -555,6 +555,38 @@ unsigned long gen_pool_first_fit_align(unsigned long *map, unsigned long size,
 }
 EXPORT_SYMBOL(gen_pool_first_fit_align);
 
+/**
+ * gen_pool_fixed_alloc - reserve a specific region
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @data: data for alignment
+ * @pool: pool to get order from
+ */
+unsigned long gen_pool_fixed_alloc(unsigned long *map, unsigned long size,
+		unsigned long start, unsigned int nr, void *data,
+		struct gen_pool *pool)
+{
+	struct genpool_data_fixed *fixed_data;
+	int order;
+	unsigned long offset_bit;
+	unsigned long start_bit;
+
+	fixed_data = data;
+	order = pool->min_alloc_order;
+	offset_bit = fixed_data->offset >> order;
+	if (WARN_ON(fixed_data->offset & (1UL << order - 1)))
+		return size;
+
+	start_bit = bitmap_find_next_zero_area(map, size,
+			start + offset_bit, nr, 0);
+	if (start_bit != offset_bit)
+		start_bit = size;
+	return start_bit;
+}
+EXPORT_SYMBOL(gen_pool_fixed_alloc);
+
 /**
  * gen_pool_first_fit_order_align - find the first available region
  * of memory matching the size requirement. The region will be aligned