[PATCH] powerpc/iommu: use iommu_num_pages() to calculate the number of iommu page

Wei Yang weiyang at linux.vnet.ibm.com
Sat Sep 19 23:04:27 AEST 2015

On PowerPC, currently we support different value of PAGE_SIZE and different
value of IOMMU Page Size.

In case the PAGE_SIZE is 4K and the IOMMU Page Size is 16M, and driver
asked for some DMA less than 16M, the current calculation would return 0
and the following allocation in iommu_alloc() would fail.

This patch uses iommu_num_pages() to calculate it.

Signed-off-by: Wei Yang <weiyang at linux.vnet.ibm.com>
 arch/powerpc/kernel/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index a8e3490..9885397 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -842,7 +842,7 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
 	memset(ret, 0, size);
 	/* Set up tces to cover the allocated range */
-	nio_pages = size >> tbl->it_page_shift;
+	nio_pages = iommu_num_pages(0, size, IOMMU_PAGE_SIZE(tbl));
 	io_order = get_iommu_order(size, tbl);
 	mapping = iommu_alloc(dev, tbl, ret, nio_pages, DMA_BIDIRECTIONAL,
 			      mask >> tbl->it_page_shift, io_order, NULL);

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