quoted

+struct dma_iommu_mapping *
+arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
+                        int order)
+{
+       unsigned int count = (size >> PAGE_SHIFT) - order;
+       unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);

The count calculation doesn't seem correct. "order" is log2 number and
 size >> PAGE_SHIFT is number of pages. 

If size is passed as 64*4096(256KB) and order is 6(allocation granularity is 2^6 pages=256KB),
 just 1 bit is enough to manage allocations.  So it should be 4 bytes or one long.

But the calculation gives count = 64 - 6 = 58 and 
Bitmap_size gets set to (58/(4*8)) * 4 = 8 bytes, which is incorrect.

It should be as follows.
unsigned int count = 1 << get_order(size) - order;
unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long) * BITS_PER_BYTE;

-KR

--nvpublic