iommu sg merging: ppc: make iommu respect the segment size limits

This patch makes iommu respect segment size limits when merging sg
lists.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/kernel/dma_64.c

@@ -68,7 +68,7 @@ static void dma_iommu_unmap_single(struct device *dev, dma_addr_t dma_handle,
 static int dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist,
 			    int nelems, enum dma_data_direction direction)
 {
-	return iommu_map_sg(dev->archdata.dma_data, sglist, nelems,
+	return iommu_map_sg(dev, sglist, nelems,
 			    device_to_mask(dev), direction);
 }
 

arch/powerpc/kernel/iommu.c

@@ -270,16 +270,18 @@ static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
 	spin_unlock_irqrestore(&(tbl->it_lock), flags);
 }
 
-int iommu_map_sg(struct iommu_table *tbl, struct scatterlist *sglist,
+int iommu_map_sg(struct device *dev, struct scatterlist *sglist,
 		 int nelems, unsigned long mask,
 		 enum dma_data_direction direction)
 {
+	struct iommu_table *tbl = dev->archdata.dma_data;
 	dma_addr_t dma_next = 0, dma_addr;
 	unsigned long flags;
 	struct scatterlist *s, *outs, *segstart;
 	int outcount, incount, i;
 	unsigned int align;
 	unsigned long handle;
+	unsigned int max_seg_size;
 
 	BUG_ON(direction == DMA_NONE);
 
@@ -298,6 +300,7 @@ int iommu_map_sg(struct iommu_table *tbl, struct scatterlist *sglist,
 
 	spin_lock_irqsave(&(tbl->it_lock), flags);
 
+	max_seg_size = dma_get_max_seg_size(dev);
 	for_each_sg(sglist, s, nelems, i) {
 		unsigned long vaddr, npages, entry, slen;
 
@@ -344,7 +347,8 @@ int iommu_map_sg(struct iommu_table *tbl, struct scatterlist *sglist,
 			/* We cannot merge if:
 			 * - allocated dma_addr isn't contiguous to previous allocation
 			 */
-			if (novmerge || (dma_addr != dma_next)) {
+			if (novmerge || (dma_addr != dma_next) ||
+			    (outs->dma_length + s->length > max_seg_size)) {
 				/* Can't merge: create a new segment */
 				segstart = s;
 				outcount++;

include/asm-powerpc/iommu.h

@@ -79,7 +79,7 @@ extern void iommu_free_table(struct iommu_table *tbl, const char *node_name);
 extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,
 					    int nid);
 
-extern int iommu_map_sg(struct iommu_table *tbl, struct scatterlist *sglist,
+extern int iommu_map_sg(struct device *dev, struct scatterlist *sglist,
 			int nelems, unsigned long mask,
 			enum dma_data_direction direction);
 extern void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist,