iommu sg merging: parisc: 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: Kyle McMartin <kyle@mcmartin.ca>
Acked-by: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/parisc/ccio-dma.c

@@ -941,7 +941,7 @@ ccio_map_sg(struct device *dev, struct scatterlist *sglist, int nents,
 	** w/o this association, we wouldn't have coherent DMA!
 	** Access to the virtual address is what forces a two pass algorithm.
 	*/
-	coalesced = iommu_coalesce_chunks(ioc, sglist, nents, ccio_alloc_range);
+	coalesced = iommu_coalesce_chunks(ioc, dev, sglist, nents, ccio_alloc_range);
 
 	/*
 	** Program the I/O Pdir

drivers/parisc/iommu-helpers.h

@@ -95,12 +95,14 @@ iommu_fill_pdir(struct ioc *ioc, struct scatterlist *startsg, int nents,
 */
 
 static inline unsigned int
-iommu_coalesce_chunks(struct ioc *ioc, struct scatterlist *startsg, int nents,
+iommu_coalesce_chunks(struct ioc *ioc, struct device *dev,
+		      struct scatterlist *startsg, int nents,
 		      int (*iommu_alloc_range)(struct ioc *, size_t))
 {
 	struct scatterlist *contig_sg;	   /* contig chunk head */
 	unsigned long dma_offset, dma_len; /* start/len of DMA stream */
 	unsigned int n_mappings = 0;
+	unsigned int max_seg_size = dma_get_max_seg_size(dev);
 
 	while (nents > 0) {
 
@@ -142,6 +144,9 @@ iommu_coalesce_chunks(struct ioc *ioc, struct scatterlist *startsg, int nents,
 					    IOVP_SIZE) > DMA_CHUNK_SIZE))
 				break;
 
+			if (startsg->length + dma_len > max_seg_size)
+				break;
+
 			/*
 			** Next see if we can append the next chunk (i.e.
 			** it must end on one page and begin on another

drivers/parisc/sba_iommu.c

@@ -946,7 +946,7 @@ sba_map_sg(struct device *dev, struct scatterlist *sglist, int nents,
 	** w/o this association, we wouldn't have coherent DMA!
 	** Access to the virtual address is what forces a two pass algorithm.
 	*/
-	coalesced = iommu_coalesce_chunks(ioc, sglist, nents, sba_alloc_range);
+	coalesced = iommu_coalesce_chunks(ioc, dev, sglist, nents, sba_alloc_range);
 
 	/*
 	** Program the I/O Pdir