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>

2 files changed, 7 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/dma_64.c b/arch/powerpc/kernel/dma_64.c
index 84239076a5b8..f9de2fddf4d6 100644
--- a/arch/powerpc/kernel/dma_64.c
+++ b/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);
 }
 
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index a3c406aca664..d0e6fac4ef42 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/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++;