swiotlb: Move alloc_size to swiotlb_find_slots

Rename find_slots to swiotlb_find_slots and move the maintenance of
alloc_size to it for better code reusability later.

Signed-off-by: Claire Chang <tientzu@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Will Deacon <will@kernel.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Author: Claire Chang

kernel/dma/swiotlb.c

@@ -430,8 +430,8 @@ static unsigned int wrap_index(struct io_tlb_mem *mem, unsigned int index)
  * Find a suitable number of IO TLB entries size that will fit this request and
  * allocate a buffer from that IO TLB pool.
  */
-static int find_slots(struct device *dev, phys_addr_t orig_addr,
-		size_t alloc_size)
+static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
+			      size_t alloc_size)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 	unsigned long boundary_mask = dma_get_seg_boundary(dev);
@@ -442,6 +442,7 @@ static int find_slots(struct device *dev, phys_addr_t orig_addr,
 		dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1);
 	unsigned int nslots = nr_slots(alloc_size), stride;
 	unsigned int index, wrap, count = 0, i;
+	unsigned int offset = swiotlb_align_offset(dev, orig_addr);
 	unsigned long flags;
 
 	BUG_ON(!nslots);
@@ -486,8 +487,11 @@ static int find_slots(struct device *dev, phys_addr_t orig_addr,
 	return -1;
 
 found:
-	for (i = index; i < index + nslots; i++)
+	for (i = index; i < index + nslots; i++) {
 		mem->slots[i].list = 0;
+		mem->slots[i].alloc_size =
+			alloc_size - (offset + ((i - index) << IO_TLB_SHIFT));
+	}
 	for (i = index - 1;
 	     io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 &&
 	     mem->slots[i].list; i--)
@@ -528,7 +532,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 		return (phys_addr_t)DMA_MAPPING_ERROR;
 	}
 
-	index = find_slots(dev, orig_addr, alloc_size + offset);
+	index = swiotlb_find_slots(dev, orig_addr, alloc_size + offset);
 	if (index == -1) {
 		if (!(attrs & DMA_ATTR_NO_WARN))
 			dev_warn_ratelimited(dev,
@@ -542,11 +546,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 	 * This is needed when we sync the memory.  Then we sync the buffer if
 	 * needed.
 	 */
-	for (i = 0; i < nr_slots(alloc_size + offset); i++) {
+	for (i = 0; i < nr_slots(alloc_size + offset); i++)
 		mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
-		mem->slots[index + i].alloc_size =
-			alloc_size - (i << IO_TLB_SHIFT);
-	}
 	tlb_addr = slot_addr(mem->start, index) + offset;
 	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
 	    (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))