+ /*
+ * DMA cannot cross 4 GB boundary. Mark last entry of each 4
+ * GB chunk as reserved.
+ */
+ if (protect4gb) {
+ entries_per_4g = 0x100000000l >> IOMMU_PAGE_SHIFT;
+
+ /* Mark the last bit before a 4GB boundary as used */
+ start_index = tbl->it_offset | (entries_per_4g - 1);
+ start_index -= tbl->it_offset;
+
+ end_index = tbl->it_size;
+
+ for (index = start_index; index < end_index - 1; index += entries_per_4g)
+ __set_bit(index, tbl->it_map);
+ }
+